Tim,

you can pretty much put anything you want into the front doors but you may need to use a spacer to keep it away from the window when its fully down inside the door...

as for rear's you have heaps of width to work with but stock 4" in the rear so you'll have to do some metal fabrication to get anything bigger in.

As for buying speakers for front and rear's unless your planning on running a competition stereo, dont bother about spending the same money on the back as you do at the front. Even some competition stereo's don't have rear speakers as they are mostly useless. I have kicker fronts (shit IMHO, they are making way for MB Quartz soon) and just 4" Audiobahn rear's which are only fillers. All running off a 600w 4 channel. And thats fine for listening to normal music at a decent volume.

As for brand's stear clear of Sony, Pioneer or Kicker.

I've heard the new JVC range and i am a big wrap for JVC, and MB Quartz are always good if you wanna spend the coin, aswell as Lightning Audio etc..

Tip is, go speak to someone at Westside or something and tell them what you want, im sure they will be happy to help you.