I Want a new system..but what 2 get??

I currently have two 12inch Rockford HE2's and a 600 watt kenwood amp. I'm looking to sell this and upgrade but I have no idea what I want to get. I want better punch and for it to be loud but clean. I have about $500-$600 to put towards this but I don't know where to start. If anyone has any ideas or knows of any good websites I could look at I would greatly appreciate it.

PS...I also want to conserve some trunk space and try to make the whole system look clean....Thanx