Best bang for the buck (and effort) ??

Upgrading to 2-10's would definitly make a noticeable difference/boost in your low end sound range. You lost me on the cross-over part and caps, if your asking if you'd need a capacitor to run subs, you'd only need one if you bought an amp, and even with just one amp, a cap is not nesecary. I hope that helps, but i can assure you that 2-10's would be very noticeable, but i can't stress enough to go with a good quality sub, if you get something cheap, it will sound cheap.

what i was wondering is whether or not the factory head unit/amp is sending a full range signal to the front and rear speakers... if so, it seems like the bass is usually the first thing to cause distortion... so in the past what i've done is install capacitors on the main speakers to provide a high pass filter so the mains don't get any bass... this allows you to turn up the head unit more but of course you don't have any bass... the sub fills in the missing bass and you're good to go... i just wasn't sure if the factory setup was already doing the crossing-over since it has a separate "sub"...

i was thinking about going with JL 10W6's... i have a single 10W6 in my camaro (in a JL stealth box) and its pretty insane... i bought that years ago, so is there anything newer that's a lot better?

thanks!

Bang for the buck you CAN NOT beat a 6.5"component speaker upgrade with 1" tweeter! A nice set of MB Quart, JL XR, Diamond Audio Hex, or Focals (or similiar, thoose are what I like) will improve your sound quality more than you would ever believe.