How much difference does a phono preamp really make?

Hi @audionoobie 
I have been a Phonostage Enthusiast and Obsessive for far too many years, where the over interest has encouraged myself to have spent more time experiencing them than any other Device in my system.
This is a undertaking that is still with me, and COVID Travel Restrictions Impacted on most noticeably, when it come to my particiapation with the social side of HiFi .

I can not put a figure on how many Phonostages I have auditioned over the years, and my interest has not wained.
Very recently, now there are new freedoms to be exploited, I was with a group of friends auditioning one of the groups selection of ancillary devices that they have, to be used in conjuction with Phonostages.
On this occasion there have been Two Phonostages, in use, along with SUT's, Head Amp's and a Deguassing Device, to attempt to keep all Demonstrations carried out with the fairest of play times for each comparison.   
On this occasion there was a Debut within the Group of a very respected and reasonably well known Brands High Level Solid State Phonostage Model, using the Built in MC Stage and the other ancillaries.

This Debut was carried out as a Comparison along side a Bespoke Built all Valve Phonostage, using a SP10R, Glanz 12" Arm and a Miyajima Cartridge.
Due to Lockdown, this was my long overdue and first encounter with the TT Set Up.
In the above case all the auditions left very indelible memories, where the impression is very positive, and is a reminder of the bar that can be set for a Vinyl Front End.
Each Phonostage shared traits that were similar, but there was an overall separation in the Presentation, where one was Fleet Footed and offered an air of precision and control.
The other took the music on and showed a Tremdous Presence with ethereal room filling Voluminous Sound.

Prior to this meeting, I was keen to get on the road and meet a fellow enthusiast.
To achieve this I carried out a 200 Mile round trip, to visit a good friends home, and was listening to their own Bespoke Built Phonostage Design.
This was not a comparison, it was a update on a Demonstration of a evolved design I was becoming familiar with prior to the Lockdown.
The TT in use was a completely Over Hauled SP10 MkII.
This updated demonstration was quite phenominal, and left me with goosebumps.
I was greatly impressed, and am very keen to hear this Phonostage on my home system.

'In a nutshell' a Phonostage can quite easily make or break a system,
in relation to how it can produce a performance that leaves a very positive impression.
The effect that the use of can have on a individual, will only be understood by being in the Company of one, preferably being used on the Home System .
Most importantly the Phonostage is a Device needing to be heard,
hearing the choices of others who have taken a long time to find their Holy Grail of a Phonostage, can be extremely rewarding and educational.

There might be foot work required to get the best experiences and gain in understanding where your preferences lean toward, but what a great way to grow in understanding, through meeting fellow enthusiasts and being given demonstrations of the choices that others have made .     

Many Phonostages share similar Topologies and when Demonstrations are carried out where a comparison is available, even if for a limititation of the time allocated for each Demonstration.

It can soon become quite evident that a selection of Phonostages sound very Similar, especially in SS to SS  and Valve/Hybrid to Valve Hybrid Comparisons.

At Bake Off's I have attended, a £300  - £600 SS DIY Build, where a large proportion of the costings is seen in the casing and casing attachments, and where a Builder will inform the audience that they had discarded a large selection of components for matching purposes, that has added to the cost,  have been witnessed to fit comfortably into the SS Category of up to £4000.

My own experience is that I have preferred the DIY Models over 
Branded Models Demonstrations costing upto £3000ish, as well as think that some are almost parity in their performances.

Branded Phonostages I have heard that are approaching the Higher £3000's can usually be seen to deliver a much improved performance and separate themselves from the Line Up.
I would think this has got quite a bit to do with the Designers 'Know How'.   
How these Perceptions would unraval, if extended listening was carried out in the Home System will also produce different assessments of the comparisons.

As said it is all about the ears as the tool to discover a preferential presentation.

I have not used a New Phonostage in my system that has not benefitted from a Extended Period of use.
Approximately 100 Hours of usage for a New Built Device seems to be  the point at which the Phonostage will come on song and appear to separate itself with a perception of a noticeable improvement from recollection of the previous time in use.

I personally feel even more time of usage will show a slightly more improved sound, maintaining a regualr use and keeping oneself familiar with the presentation, will be enough to reveal these later shift in noticeable changes to the Sound Quality.

If a Phonostage is heard as a New Phonostage and offers a impression that is a wanted experience, then the liklihood is that after a Period of usage the Good Impressions already made, will become even more substantial.

I am in a habit of inquiring how many Hours the Phonostage has been in use for when I discover a presentation that is to my preferences.

Something Similar happened during 2019/2020 with a Cartridge I had rebuilt.
It was initially compared with very few Hours of usage to Two other Cartridges from the same Brand in a friends System.
The Comparisons were able to be undertaken using the Same TT> Tonearm  > Head Shells.
The Two Cartridges had 100ish Hours and 300ish Hours of usage.
My Cartridge was brought back to be compared at approx' 50 Hours,
100 Hours, 200 Hours and 300 Hours.
At the visit with the 200 Hours of usage my Cartridge was very noticeably inproved during the comaparison and One Cartridge was sounding a Lesser Performing Cartridge and the other Cartridge, which was a Top of the Range from the Model Range during its time of production was being very closely matched in the Performances with my own Cartridge.

Both Cartridges have not changed in any noticeable measure since the 200 Hour usage comparison.

Maybe not in all cases, but it is worth inquiring about the Hours of usage when a Cartridge is being auditioned, as there will be a time when it is heard at it Prime, especially when the Cartridge has received a
100+ Hours of usage.          

There are always going to be wide differences in experiences and opinions in the methods used to produce a Vinyl Chain in a system. 

Individuals who are enthusiasts and prioritise the use of Vinyl LP Media, can have accumulated multiple years of usage and replays of Vinyl,  along with a accumulation of experiences of using different ancillaries to create an experience that is satisfying and to their unique preferences. 

Myself and some others have come through times when options on Ancillaries were vast and quite affordable.
The period in the 90's when Vinyl ancillaries were looking like disposable items, and the Used Sales Ad's were commonly seen with the recently produced items selling for extreme reductions.  

The variations I have seen in a Vinyl Front End and down stream set ups, has been of interest to myself, and one area of choices being made,
I have noted on numerous occasions, is how many individuals I have been fortunate to have met and have become friends with, have been users of different TT's Models with different motor drives, different modifications,  and the use of differing Plinth Materials and Designs.

Then there is the differences in the selection of a Tonearm and the use of a Tonearm, some will not settle for one Tonearm, additional options must be catered for, and methods to mount more than one model will be produced.

Then there is the use of a Cartridge, putting MM, MI or MC to the side,
some owners are with a vast collection of Cartridges and like to have a few mounted in a Head shell ready to go, (some are also only used mounted on a particular type of Head Shell) and others like myself stick close to one favoured model, and may have a substitute Cartridge to assist with increasing the longevity of usable life of the most preferred Cartridge. 

From my experiences gathered, I am not at any time, meeting with others who have an identical set up, they genuinely vary quite vastly and are occasionally seen as a reasonably close in a match, for the Front End ancillaries that are Selected.
If down stream from the Source is added into the permutations then I have not met with anybody doing similar things with their choices to produce a Vinyl Chain in a system.
The choices selected for SUT/Head Amp > Phonostage > Amplification > Speakers is always different. 

The OP is sharing in a likeminded enthusiasm for producing a Vinyl Chain in their system.
When the discovery is finally made of their preferred Set Up, it will again once more be most likely that it will be unique to their wants and not many will be discovered to be reciprocating/ mimicking the permutations of the choices made for the ancillaries that are in use.   

The OP has decided he has to spend monies to discover a presentation that is perceived as beyond the performance available at present.
The question of how much budget should be allocated is commonly going to be met with contentious debate.
Most importantly in most cases, monies have to conform to a Budget, and achieving the best value for the allocated monies, has to be the priority.
In my view the best value is not the item acquired at the best price, but the item acquired, is proving to be a highly satisfying inclusion to the system.  

A Cartridge is already acquired, and this route has been reported as worthwhile and quite satisfying.
This Cartridge would be best allowed to have approx' 100 Hours of user time to allow it to settle in, then the value it is offering will be realised when used in the system as is.   

Will buying a Phonostage without any prior experience of the ancillary, allow the New Cartridge when 'settled in' to really show of its capability ?

Demo's of another ancillary in the system such as a Phonostage is looking like a practice worth pursuing.