Brother, I use an 8" and it kills it for what Im doing. And these get rave reviews by people sying it blows away their old 12 inch.
Skar Audio 8" SVR. 400 watts RMS...like $75.
Im running mine at 4 ohms with the Skar rp1200 watt amp. It puts out 500 watts at 4 ohms so its perfect