I installed the 330uF 65v caps this afternoon, and the improvement is amazing. They didn't quite pass my "Dark Side Of The Moon" test, but I'm still pleased. I also bought a pair of 220 uF caps, but my guess is that they would probably make the door speakers sound too thin and pump too much through the subs. As others have said, I think that something around 270-275uF would be just about perfect. I have had difficulty finding non-polarized caps with that rating, but I'll keep looking.

My installation took about 5 minutes per side. I used the Hot Line Quick Splice connectors, which should make it simple to experiment with different caps.