Pass labs krell parasound amps

Nelson Pass has a long history of designing reliable  & wonderful amps.  I owned a 
Threshold 4000 for 25 years before selling it and buying the X250.8.  Yes, they run hot & yes, the X250.8 does have the "Pass " sound, which makes it very easy to enjoy and live with.  Once you own it I cannot imagine an unhappiness UNLESS you are one who continues to compare A to B....on its own it is great....additionally, you will be hard pressed to find a company with better customer service, though I doubt you will ever need it...

Personally, I would stay away from Krell until they get their house in order due to the loss of one of their founders.

Pass and Parasound are bullet proof with excellent customer service.  I have no experience with Mac.

I moved from a Benchmark AHB2 to an Accuphase P4600. Yes the Benchmark had a sharpness in the lower treble but also a powerful base. It’s still a real bargain if paired with the right speakers that are very warm. Even with my Harbeths I still found it a little too cold for my taste The Accuphase is just very musical, live and refined. But expensive. If Accuphase is in your price range please audition. Plus their Class AB amps run only slightly warm. 

Of what you listed I would choose Pass labs.  Excellent products and support.

I have had Pass Labs, Parasound, a lot of Adcoms, Gryphon, Classé and probably some more. Then I discovered Krell for about 20 years ago. Started with KSA 150 then five more KSA 150 (have a total of six), one KSA 250, two FPB 300cx and four KAS2 monoblocks. I also have had Krell 300S but that was a short visit in my house. The Krell S series sound does not suite me. I only use Krell preamps like KCT, a couple of KRC-HR, KRC 3, KSP 7B etc. My speakers are solely old Infinitys IRS series (Beta and Epsilon) and RS Kappa series (a couple of Kappa 9 and 8) They are hard to drive but my Krells that I use every day have absolutely no problems with them. The sound is warm, detailed and the Krells can deliver very much power. Very important is that the Krells manage to sound warm, detailed etc even at low volumes with my speakers. I think they are the only ones of all poweramps that have manage to do that. For my main system I use four Krell KAS2 monblocks, second system I use two FPB 300cx, third, fourth system is different combinations KSA poweramps. (bi and tri-amping. I used to have a pair of Revels, dont remember which ones, medium size and price, and every single one of my Krell poweramps (except the S series) handled those easily. Probably nothing wrong with Krells S series but I found those to analytic and lacking a bit of "warmth". Within Your budget I would go for a pair of freshly recapped Krell FPB 750 MCX. I hardly think You will be disappointed. Good luck! (I have absolutely no interests in the Krell brand or company. I am a Swedish lawyer who just love the sound of Krells)