I am enjoying my analog system, but what can I do to improve?

Sealed box speakers work well for me in a small room. I have heavily modified Yamaha NS-1000m. Now semi active, with replacement Scanspeak 12" bass drivers. Incredible bass depth, detail and control in what is a poor room. Not boomy at all, even at high levels. The Yam Beryllium domes are legendary and do the mids and top end justice. The stock Yams need careful amp matching, or they can sound top end forward.

I've had a few SL-1200's, its ok, but not a brilliant deck, lightweight platter and the bearing is only adequate. I've done many, many mods over the years, including Hot Rodded Rega arms and a Transfi Linear tracker. To me this is the weakest link and rather than try and upgrade it, I think a different TT/arm is where you should start. Possibly looking at speakers, better able to work in your room, as a second stage.

If you want realism, on anything other than small group acoustic. You need depth and dynamics. In a small room this is difficult, I've found sealed box is the only way to achieve this and retain any kind of control or quality to the sound.

The speakers and how they interact with your room is a critical factor. A "good" speaker may not be good in your environment. You have some nice bits of kit, I feel the room has to be seen as an issue and dealt with appropriately. Fundamentally the speakers, or rather type of speakers, will have more effect than any room treatments you apply. This is presuming there is some form of floor covering and furniture in there. My choice for your environment, best to worst would be:

Sealed Box

Panel

Ported

Open Baffle (due to space requirements).

To the OP

After writing two lengthy posts that both got lost in the either, I've given up.

Take a look at my Technics projects, a lot of work that made only a small improvement. https://www.jkwynn.co.uk/Projects.html

This is why I say try a different deck, don't take recommendations, try and listen to other set ups and buy something you like the sound of, is the best advice I can give.

The Sound Lab are god speakers, I just question their suitability in your room.

@chungjh 

"So are you currently happy with the modded Rega P10?"

I'm not sure if this was meant for me? as I can't see mention of a P10 by anyone.

My Rega Arm was fitted to a modified SL-1200 mk II. It was an improvement on the stock arm, but not night and day. It required extensive work/expense and after the experience, I would say not money well spent.

The modified Technics arm project, using a straight Aluminium tube inside a Carbon tube was also only a very small improvement over the original.

The deck with the linear tracker was a larger improvement, but there were so many mods, the only thing remaining from the Technics was the DD Motor assembly/PCB. Advanced DIY skills needed for the deck and again I wouldn't recommend going that route.

I've started looking elsewhere, to idler drives, which can have their own issues, but building the decks is a hobby for me and I enjoy the making. Not everyone has the skill, tools or time to do the same.

The Technics deck is almost an over achiever, it works very well as is and not much in the way of performance gains can be had, from the many expensive mods that can be applied. Gains are only relatively small for the outlay, which is why I think your money would be better spent elsewhere, if you want bigger differences. Expect to pay for that though.

The Audiomods arms have great value/performance ratio but deserves a better deck.
The Schroeder string and magnet design, if done as a DIY build has huge potential, or for a ready made, start at around £2.5k if memory serves.

@rauliruegas 

You've been reading the marketing hype.

The SL-1200 Mk II and SL-1200G are remarkably similar in performance, my source is Technics own spec sheets and in some areas the MkII measures better.

For most comparisons performance can be classed as the same.

@rauliruegas 

I can appreciate there are differences in the motors, the start up torque is higher on the new one, but start up time is exactly the same. Basic speed stability, wow and flutter is no better (worse). The literature talks about cogging, everyone knows this was marketing hype by the belt drive brigade to try and undermine specs they couldn't compete with, when DD first appeared. Technics seem to have jumped on this as a way of promoting the new motor. But basic common sense tells you, they could not achieve such high levels of speed stability and wow/flutter figures if cogging was real thing. As for the arm, they changed from one alloy to another for the tube, same plastic yoke and crude fixing method, whoopy do.
Sorry, we'll just have to disagree on this, for me the price tag is just way to high and the attempts to talk up the spec just don't stand scrutiny.
Its a good deck, always was, but you soon hit a performance ceiling when trying to upgrade and you need to jump ship to improve further.
All my opinion of course, but that's what was asked for.

I'm sure the OP will take all opinions into account and make his own mind up.

This is off track from the question of how he can improve what he has.

Am I missing something? what's the big thing about the new Coreless motor.

All the Technics DD turntables are Coreless are they not?

They have produced many variants on different models over the years.

Where is this extra build quality people are talking about?

Not in the motor build, not in the platter, not in the bearing, not in the arm. These items are of similar construction.

They made minor changes to what was a well respected deck to justify the higher price when re-launched. Take any of the elements and do a side by side comparison. Although we are told it is better quality, re designed from the ground up, there are no meaningful details of any of the upgrades. Look at the two main bearings, exactly the same principle and crappy sheet metal plate supporting the thrust pad. They stuck a brass sheet on top of the platter, many people use Copper.
I'm not saying the late models aren't slightly better sounding than the earlier ones, just put things in perspective, they are very similar construction and performance from what I've heard. Never heard a like for like comparison in the same set up, but I've not had my socks blown off by the latest models when I've heard them hooked up to decent kit.

I think that's all I've got to say on the subject, people can make up their own minds. But in terms of design and build quality, I would prefer a good used SP10 any day of the week.

If the rest of the system is capable, the SP10 has weight and authority, bass is well defined and timing/separation is good. Basically high on PRAT. Again its not massively better. The 1200G is a good deck, to step up from there you need to be looking at serious kit. The laws of diminishing returns means improvements will be small, but costs will be high.
And a well set up 1200G will always sound better than a poorly set up SP10 of course (Arm/Cartridge dependant).
For anyone starting without a Turntable, or stepping up from a modestly priced one, the 1200G represents a large outlay. A  previously owned SP10 has more potential in my opinion and a decent example of a MkII could be had for a lot less money.
If you already have a 1200G then this would not be a good move financially and more of a sideways step performance wise.
I heard a Mk5 and SP10 in the same set up, both good examples, with decent cartridges and arms. The SP10 was slightly better but not by much.
Though, to be fair, Mk5 had bearing, power supply and platter upgrades.

@lewm 

My position is that the newer and top range decks are better, but not massively, each step up is only very small, because the the original was so good in the first place.

Arms/Cartridges and accurate set up will have more impact and if you modify an older deck, upgrading bearing and platter it can compete with the top models anyway.

Cogging does not effect the sound in any meaningful way. Speed stability is what counts and this is VERY good on all models. It's easily measured and is at similar levels across all models. Cogging effects torque and it is difficult to see how fluctuating torque has any audible effect.18 changes in torque per revolution is a fact, but what effect, that has on performance has always been the question. (18 is from memory).

As has been pointed out we've drifting off track from what was asked by the OP.

I think the front end is the weakest link, followed by the speakers (in that environment) Views which haven't changed.