You might want to re-allocate the money spent on the rear speakers for a really good 6.5 Componet set. It will sound better in the end beacuse your sound stage will be infront you not behind you. Notice when you go to a concert how music is infront you not behind you? Theres a reason for that. With that in mind I'd look to myself some Diamond Audio Hex 6.5's. For the woofer I'd get a HSU audio. Some info here... Dr. HSU makes a 12" sub which produced 121db inside a convertable. The subs are almost identical in design to the Image Dynamic ID's and sell for aprox 100 dollars. This system will sound much better than trying to produce your midrange from behind your head. This is why a lot of people run no rear speakers in IASCA SQ class.
For $500 bucks you could get a pretty sweet sub. Are you partial to 12's or is that just cause they're the most popular size? I went from 2 12W6v2 to 1 10W7 and I won't look back. Agreed with above that you should just focus more money towards some decent component door speakers than getting 6x9's. You'll get better sound quality out of round speakers anyways, plus you're going to have to do some custom fabricating to get those 6x9s in somewhere. Actually, firt off...what car are we talking about here cause that would make a large difference. If it's an MK3 then go with better door speakers cause the rear speakers pretty much just shouldn't even be there...but they are and they're freakin tiny. A shallow 4" is pretty much all you're gonna get back there comfortably.
its a 1997 camry. I was thinkin about doin one 10w7. I really dont care about size, i just want the best sound quality. 6x9's go in the back. nothin custom i have 6.5's in the front and 6x9's in the back. I have a huge trunk so i can fit alot in there!
If $330 is expensive for those hex's then I don't want to tell you what I payed for my 5.25 Focal Polyglass Components...Well since you're doing the Cam, I would say get some alright 6x9's for the rear cause they can take a beating as I've learned in my "pre-sub" days. They just aren't "as good"*personal preference* of sound quality as circular speakers. Because you have a huge trunk, use it wisely. Build a good box that will take advantage of the airspace you have available, but won't be outrageously large. The 10W7 is a great sub, I have had absolutly no regrets with it. The shop I go to back at home recommends those over the 12's just cause the sound quality is better. The 12's hit like a freakin beast, but they also need lot's of air space. As for websites, if you are starting to find out what brands you like and the models you are interested in. Throw them into Froogle and you can get decent price quotes on them, if you're looking for good deals that is.
for the sub go w/ the JL 500/1 it's a real good match up for it. Amp for the mids and highs...it's up to you, I have the JL 300/4 and it works great also no need for Caps HU is all up to you, if you want it to do tricks and have all the bells and whistles go for it cause it's only going to fade(granted you have three sets of RCAs) and read CDs since you are using the amps to power your speakers. I personally like eclipse, they're simplistic yet very good quality and you have a seperate sub level controller for those days where you just don't feel like turning your brain into jello