I owned a Krell KSA 250. I thought it was wonderful. Very real - and believe it or not - nicely warm. It will also handle any speaker you throw at it, in the future.
Never heard the Audio Research but I owned the KSA 250 for 5 yrs. I got it for my Duetta Sigs but when it was delivered I couldn't move it to them so I hooked it up to my Merlin VSM just to see if it survived the shipping. Wow. I didn't think it would be a good match, usually its Merlin/tubes. Bigger WOW on the Aps. I think it's a really special amp and you would certainly be future proof with any speakers. You may ultimately find a better synergy with another amp and that's just part of this hobby. I ran mine off a normal 15 amp circuit. It does run hot. It's problaby close to 15 yrs old and may need caps in the future. Good luck.
ARC will be your best bet if you have any reservations about listener fatigue, or if you value transparency and imaging. ARC can be gorgeous, which is not to knock Krell, but ARC done right (right model in the right system) is magical. Good luck
I am a very satsified Krell 400cx owner but in this particular case I agree the ARC will likely work best for you in this application. I am also a tube lover but I could not drive my Thiels with it. Happy listening.
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