I bought RED Sony Xplod speakers for my 1993 Viper. Looks cool with the red car.
They are 6,5" with tweeters. You have to "massage" a bit the inner doorpanel, since the old speaker is propably a 6". Just cut a bit and it will fit. You do not have to cut the complete hole.
Tweeters are a direct fit.
Sound? Its Ok, not really enough bass, but it makes enough noise for my taste. For the bass you need to sacrifice the passanger foot area, well, at least part of it. I left the original amps in place. I do like the sound, definately better than the old speakers, mine had 1/2 of the rubber gone anyway..
Try with set of nice speakers, if you are not satisfied, go with sub or amps.
Lauri