cooling my Krell monoblocks

You let a cat spontaneously combust. Could you be anymore illustrative?? My word !
As for the fan and clicks ask Krell to tell you what you can do beside ignoring it which you can't. Be very firm and ask them to get an engineer to tell you that you may or may not use the fan . The big McIntosh amps had fans and may still but as the others have said the Chinese Oops I mean U.S. engineers have taken that into account. Just don't use ice and don't let a cat get toasty on the amps that would warm them even moreso.
Another idea is to go back to the 250s if they had enough juice for you. I bet a whole bunch of click loving 250 owners would trade up for 350s.
BTW who or what is Krell is it a derivative of an English root. I know Baleen whales and Whale sharks etc. eat "krill" a tiney shrimplike sea creature. Krell is owned by an Italian American. I think his is name Dan D'Agostino.

What is heatsink tape made of? If it is conductive you really should let Krell place it, otherwise you could be one hairball away from tradgedy.

It's odd the way that audiophiles do just the opposite. They think that their stereos don't sound as good as they could and relentlessly try to improve them. For many it's a futile effort to achieve something they have already, great sound. The average system that an audiogon member has sounds good, period especially when viewed on an absolute scale. The top 1% of all the sound reproduction extant I'd venture. Is it Krellian perfection? No and never will be for many.
Me- I am happy... I think... you know the other day something just didn't click (pun).....the sound no longer ...I might need to...roll the tubes again... no it's those analytic speakers biting you again ... no it's....the room but ... Oh no