I'll give you some suggestions on what speakers to use for front and back, I don't really know alot about subs and amps so ill leave that stuff to the experienced.

High priced suggestions:

MB quart psd 216 comps 6.5 inch up front- $215
Infinity kappa 3 way 6x9s in the back- $135
An amp with at least 75 watts rms going to each channel- Probably anywhere from $300-$500

Budget suggestions:

Infinity reference 605cs 6.5 inch comps- $105 (i use em on 17 watts rms and they kick arse!)
Infinity reference 6953i 6x9- $88 (I have these too and they hit pretty freakin hard for 6x9s, and give great highs)
An amp with at least 50 watts rms going to each channel- $100-$300

Oh and for the radio- If you like using mp3 cds go with the alpine cda-7894 (~$300), if you are more into regular cds and cdrw go with the Clarion ProAudio DXZ825- (~$220) (dual 24 bit DACs baby!!!!)