if you need help designing a system, id be glad to help you out, i have built quite a few ranging from competition quality spl setups to sound quality setups, and used about every decent speaker brand in the business.. you dont need to spend a ton of money to sound great, most of the big name speakers are overpriced junk truthfully..
in order to design a sound system for you we would need to take measurements of the vehicle, decide ported or sealed enclosure (you get smoother bass response in a properly tuned ported enclosure, and can sound every bit as clean as a sealed enclosure.) size and amount of woofers, and then go from there.
after you pick out what you want the enclosure to be, build around that, components, amps, etc. if you're not planning on going too crazy with power, i would suggest doing the big 3 upgrade which is replacing alternator wire, motor ground, and battery ground with larger wires. if you are planning on tremendous power, consider a second battery (dont even waste your money on a capacitor, they are worthless)
at any rate if you want to seriously discuss your options, feel free to pm me and we can set something up.