One suggestion -- rather than spend big $$$ (and effort) on replacing caps with expensive variants -- an endless chase -- take a good look at Neurochrome amps:
www.neurochrome.com. Those amps are
much better than the ones you have listed and won't require the time/effort to modify. Plus, after you spend all the time/money on the caps, I bet the net cost is about equal. And you'll end up with a much better amp to boot.
Read about Neurochrome on their website and read comments on DIYAudio. You can thank me later.
Best, -dGB
P.S. Just re-read your post. If the boards are already a sunk cost for you -- looks like that is the case -- then, as Emily Latella used to say, "Nevermind".
