Well, what I would do in your car would be to put as much work into the front setup as I would with the subs. The reason is that you stated that you are looking for SQ and the way to get there is have mids/highs that complement your subs.
I am a Directed Audio man. You know, those that make Viper and Clifford alarms? I'd go with 2 sx 12" subs in a ported box about 2.75 to 3.25 cu/ft with a rectangle port tuned to 38hrz. Those to be ran off a D1200 amp (be better if you can afford the d2400). Then you should get csx650 6.5" componet sets to be ran off an a502 amplifier. For a head unit, look for anything that's got decent responce with many adjustments for sound. I love the higher end JVC and Pioneer stuff for the money but Eclipse is an even better unit. The Eclipse can take you over your limit alone.
I did this setup for a local kid and he was estatic over how well it sounded. For the time being, he just bought a cheapo Pioneer from Walmart but it sounded great. I guess his buddies liked it because now they're hanging around the shop.
You should be able to find a dealer near you at
www.directed.com if not, PM me.