well....... $200-$300 for speakers and amp. The 5 channel amp idea sounds good to me. so lets go with that for right now. Comps are still very much out of this too.
im not sure what fits that car. I dont know much about the car cause its not mine but i look on crutchfield and it said that 6 1/2'' would fit but it also said 5 1/4'' would fit too so im confused.
You should be able to find a diamond audio D3 400.4 on ebay for around $125 or so (I don't have access to ebay at work)
You can talk to Don (6speedcoupe) and get some ArcAudio coaxials for around $75 each or so (Don't quote me, I bought some 5.25s for my GF and I think they were around there, but I don't remember)