Upgraded from 2 10" subwoofers to 2 12" subwoofers. I decided to try the $30 Dual sd12 subs from walmart... They sound good to me and move way more air than the 2 Rockford Fosgate HX2s. Damn good deal for $30 IMO. I bought 2 more so I'm going to build a box behind the back seat with all 4 in a row. I just need to get a new amplifier and run them off about 800 watts.