If the Krell KAS are the huge two piece mono's connected by solid copper (or brass?) bus bars that went for around $35K back in the mid 90's, then I have heard them extensively in various setups along with the KAS-2's, various KSA amps and all the FPB series. I have not heard many of the latest amps, and certainly not the Krell Evo series, but the KAS mono's were easily better than any of the FPB amps and remain perhaps the finest amps I have ever heard...amazing.
I did not care for the KAS-2 as they were very much like the FPB-600's - flat and lifeless (the FPB-300 too). Just my opinion, of course. For reasons others have mentioned, unless the price were too good to pass up, I do not believe I would purchase the KAS mono's due to complexity, age, and likely astonomical cost associated with repairs. I really do not know, however, and am just speculating: for all I know the amps might last another 100 years...they sure looked like they could.
I did not care for the KAS-2 as they were very much like the FPB-600's - flat and lifeless (the FPB-300 too). Just my opinion, of course. For reasons others have mentioned, unless the price were too good to pass up, I do not believe I would purchase the KAS mono's due to complexity, age, and likely astonomical cost associated with repairs. I really do not know, however, and am just speculating: for all I know the amps might last another 100 years...they sure looked like they could.