Try them in a bigger sealed box or a custom ported box on 500w a piece. Otherwise google your question so you will get a better answer. If you would've used the search feature u wouldn't of had this problem.
An yea they a cheap subs in a cheap box with a cheap amp 500bucks doesn't get you much. But if u can build boxes you can get decent. The box will make or break any sound system. Equipment means very little with a good install. But u still have to realize that you have bottom line subs