if the rest of your system is alpine and eclipse, id think youll want better subs than those. thyre OKAY as ENTRY level subs.
do you want more sound quality, or loudness?
im pretty happy with my infinity reference 12s, and i got them for 60$ each, for the price, i like them. however i realize there are plenty of better subs out there, probably some even cheaper as well. just take your time and look around before you purchase