I recall when looking at the block diagram for the factory amp connections that the speakers were labeled as 2ohm, which would make the calculations incorrect up to now. That being said, from everything I've read 270-300uf caps seem to sound the best (as reported here) so that's what I'm looking for at Frys. I work in Silicon Valley where there's all kinds of electronics bits and pieces stores, so if Frys doesn't have them someone around here will.

Are the tweeters cap'd or are they also running full range?

I wonder if a good two way mid/tweeter crossover wouldn't be the way to go, but good luck finding one for 2ohm speakers. Orion made some awesome 2 ohm component speakers with a supurb crossover network some years ago (I have a set, and their incredible). Unfortunately the crossover is probably as large as our OEM amp, so it would be difficult to install, and it's one crossover box for the mids and tweeters, not one box for each side, adding to the complexity of the install.