For the speakers I would highly reccomend Alpine 6.5". You can choose the model based on your wattage and spending constraints, but the 6.5" Alipine SPS600 80W work great for me! I am pushing them with an Alpine F200 200W (4 channel) and they sound beautiful. Keep in mind that they are not meant for bass output though (that's what subs are for) but they sound very crisp and handle mids/highs excellently. The pair goes for under $100 for sure.
If you are looking to save on costs on a frontend, I would suggest checking out Driveline! It is still under development but right now it's looking pretty great (and it's free).
Check out my project too =) http://www.mp3car.com/worklogs/15065...k-box-1-a.html