I'd go with some Focal's.
6.5 "Focal Upgrade Special" from
www.zalytron.com - $130
Soundstream Exact 5.3 X-overs from
www.partsexpress.com - $30
Total Cost - $160
Incredible mids and great highs. You'll want a sub in your system, though, as the bass is a little weak. And, you can only surface mount the tweets.