Congrats! I noticed an improvement myself, basically did the same thing as you, replaced the 6800uf caps with 10,000uf.
Another thing you can try is to remove the 30Hz boost, or reduce it slightly, if you find that the amp runs out of steam or 'clips' when pushed too hard. I would rather have no boost but cleaner bass at 30Hz with more overall headroom, than the 30Hz 6dB boost, which basically sucks 4X the power at 30Hz and quickly clips the amp...
After i did that, the plate amp was much cleaner sounding. That was probably the difference you heard between the plate amp and your power amp driving the sub.
Gd luck!!
Another thing you can try is to remove the 30Hz boost, or reduce it slightly, if you find that the amp runs out of steam or 'clips' when pushed too hard. I would rather have no boost but cleaner bass at 30Hz with more overall headroom, than the 30Hz 6dB boost, which basically sucks 4X the power at 30Hz and quickly clips the amp...
After i did that, the plate amp was much cleaner sounding. That was probably the difference you heard between the plate amp and your power amp driving the sub.
Gd luck!!