Hello JJ,
johnyboy's advice about doing the cap and grid stopper changes first is sound advice. Get a good feel for how your amp will now sound ( I've done both mods and the differences from either are not subtle ), before going further. Please understand that the ASC's also benefit from breakin, but I found them to really smooth out after approx 15-20 hours.
From your post it appears you are changing one PS cap for an ASC. If that's true, which one is it. I've done all three, but changed them one at a time, starting w/ the filter cap, then the output stage decoupling cap, and finally the input stage decoupling cap ( 15uf ASC ). The sonics improved w/ each change, but when all of the electrolytics go, the difference is dramatic.
Someday you might want to think about getting the last electrolytic out of your amp, the cathode bypass cap on the output stage. First I simply removed mine and left the 100ohm resistor unbypassed. The sound changed. I lost a little gain; not much, but I did have to crank the volume control just a bit, and the noise increased a tad also. But the sound also changed, though very slightly, and I really had to concentrate on specific things to notice a difference. It seemed just a tad cleaner, but also drier, i.e., maybe just a tad more detailed. I preferred the amp w/ the bypass cap in place. But that's me, YMMV. Try it and see what you think.
I then put in a 100uf ASC cap in an Ultrapath connection instead of the bypass cap, and this baby's staying put. Noise did increase, but I knew it would. If I wasn't going to build a new amp w/ a much cleaner PS than the Zen, I would modify the stock Zen's PS configuration to make it quieter and keep the Ultrapath connection. That connection makes a very significant change to the character of the amp.
Well, have fun and be safe in there.
Cheers, Crazy Bill