ofoofoo .. sub is always best for bass .. can't be beat with normal speakers ... if u're stuff for space ... go a 10" ... as for amp ... if its just for bass .. then get a monoblock amp ... they are designed just for subs and they are much more efficient for subs than a normal amp so u win with price/performance there ... i'm currently running my splits of the head unit right now and it works pretty good ... but if u really want it to sound good then get an amp ... an example of a good cheap system would be a cheap alpine monoblock ... about 300 ... 10" alpine type S ... thats about 150 maybe .. 50 for the sub box if u make it urself ... that will give u good bass ... forget the back speakers ... spend big on the fronts ... that will be a killer system .... good luck