Intg Amps: Hegel 590 vs NAD M33 Masters vs Gryphon Diablo 120

Of the amps you mentioned, I have heard two and they are very different. ( Hegel and NAD)  Great, but different. Unfortunately, it was an apples to oranges, different dealers and rooms listening.  I have a real soft spot for Hegel and not for NAD. The NAD is supposed to be a Purify, but I was not impressed. Maybe all the digital stuff in front. Don't know. Maybe I like the distortions from the Hegel. They were on Wilsons which are pretty good.  I heard the  NAD on B&Ws which I do not like at all. Don't get me wrong, both are serious great units. Just my preference. 

Your weakest link, kind of stretching to call it weak, is probably your RIAA stage. 

Do look at the actual bitrade of the files you are streaming. They may not be as good as you think. 

Have you considered an outboard DAC?  I am not sure the Hegel ( or NAD) internal is as good as it could be. Not bad, but not great. I auditioned the Hegel with a Qutest, the NAD with it's internal. 

Room correction can be critical, but do you need as complex as Dirac?  My room is too bright and being a LIVING room, no treatments are forthcoming. I put an Antimode on the sub ( single family so I can run a sub) but on the mains, I find just a traditional tone control to balance very nicely. My speakers are pretty flat in free space.  I could do that in JRiver, but I find some CDs I need to adjust a little so for now, old school tone control for the treble.  Your brain will "pattern" the room and unless things are really bad, fix a lot of EQ issues. You get used to it, or as the subjective reviewers say, the "electronics needs weeks to burn in". Really, it is their brain adjusting. Dielectrics form in hours, not weeks. 

Gryphon by miles

I can contribute that I have owned the H590 and found it a formidable amp.  Plenty of power, a DAC that reviewers gush over, and Hegel's design philosophy that the amp should add nothing to the sound.  It is smooth and neutral.  I would look for one slightly used.  Only sold it when I decided to move up to the H30.  

In general in this pursuit you get what you pay for… particularly when you get to the ~ $7 - $10K or above. These are professionally designed, well reviewed and must be sonically of value or they are not going to sell for long.

Bringing in an audiophile component into your system will likely give it a big boost. My rule of thumb is you need to jump at least 2x in investment to get a clear and substantial improvement. So, I think the Gyphon meets that criteria.

However, you are talking about a system. While you can absolutely make good speakers sound great by investing more in electronics. In the end, you have a system and to have it perform well you need all equal performing carefully chosen components .

My rule of thumb in investment is 35% speakers, 15% streamer, 15% DAC, 20% preamp, and 15% amp. It is not a hard and fast rule. But I have gone through half a dozen upgrades over the last fifty years and usually ended up about there. My current system is $32K, $22K, $17K, $17K, $22K respectively… as an example.

Those of us that are really passionate about this tend to plan our upgrades to a new level, although it may take several years to get there.

I hope this is helpful.