I want two subwoofers, leaning towards 10's rather than 12's.

This is just personal opinion, YMMV, but I agree with you in this.

With the exception of some astonishingly expensive 12's in a very serious competition car (Est. $60,000 in the stereo system) all of the 12's I have listened to seem dark and boomy, virtually atonal, just thump thump thump.

A good set of 10's on the other hand can actually be melodious, contributing to the warmth and ambience of the system if you are courageous enough to cross them over at a high enough frequency. Again, this is just my opinion and people who know a lot more about stereo than I do will disagree with this, but I have found that running such a high frequency through the subs that they almost certainly are distorting adds a warmth and presence to the sound that I really like -- and quite a few IASCA judges have agreed. I'm guessing that in my car at least (it's a Taurus station wagon) with the subwoofer nearly eight feet behind the listening position, the distortion may be just getting lost in the rest of the sound. Not a purist attitude, I know, but I'm happy with the end result.

Finally, a pair of 10's is a lot easier to fit into the car than a pair of 12's.

tanstaafl.