Here is my recent experiment with an Adcom amp(GFA555II).
Sound was blah, lots of power but no finesse, which was why I mainly used it as a bass amp... bypassed the input cap with a .01 teflon cap(just because I had them), and man, it totally transformed the sound, lots more air, and detail I never expected to hear. Zero grit.
But I could still hear the "print" of the stock cap. So decided to pull the original cap and replace with a Sonicap. I have been running the amp 24/7 for the past couple weeks, and can state that the input coupling cap Adcom uses are total crap, it was even undersized, rated at 50V whereas the schematic called for 100v.
So spend less than 20$ for some bypass caps before spending hundreds$$$, you may just be surprised how good that Adcom amp CAN sound. Oh yeah and change the captive power cord too for more 'umph'. aa
But wait...you are the guy that's rollin' in money? Never mind then, go forth and stimulate the economy.