You can't really get low bass without subs but you can get decent midbass, with some work. You need to apply sound dampening material to your door panels to stave off the resonance and vibration, then install 6x8 coaxials or components or 6.5"/6.75" coaxials or components. You really need an amp to bring out much bass at all but the speakers need to be able to handle the amp. Cost depends on quality and setup/installation. Easy to do yourself. The sound dampening material for your door panels is expensive but a must if you want any good bass without a subwoofer. The resonance/vibration of the door panels from the mid-bass cancels out the sound. If you don't have a good aftermarket headunit, it's almost a must for good sound.

examples not counting wiring or sound dampening -

http://www.crutchfield.com/p_065PRO6...ml#details-tab

http://www.crutchfield.com/p_500MRXF....html?tp=35782

or

http://www.crutchfield.com/p_236TN573/MTX-TN573.html x 2 sets

http://www.crutchfield.com/p_777M405....html?tp=35782