I put in the infinity kappa 1200w's today, they sound really good for a under $100 subwoofer. Sound much cleaner than the Pioneer champions I took out and don't have hard time with certain bass notes. I still need to clean up and cover the spacer with carpet or vinyl. Happy with the Kappas, more SQ sub than spl, but at 52, I enjoy good sound more than all out spl. The box I bought from a member here, was like $20 plus shipping and is fiberglass he made himself, super thick and strong. For super budget build, I think it sounds great. Now I just need to finish off the sound deadening, closed cell foam, add the 6.5s to front doors and possibly tweeter to overhead and I am done, all parts and supplies I have already. My total into this setup is pretty cheap, box under $200 shipped, can't remember exact number, may be $150. 2 12 inch Kappas 1200w $96 each. Rockville db14, 1000 watts cea rms, came with install kit, $135. Amp pro ch41, $135 open box, Gx302 for dash, $49, infinity 3022cfx for center, bought open box at Crutchfield and came with 1 set of harness, bought second set from them, total for the infinity open box pair and harnesses $50. Door harness $16 for 4. Jbl power series 6x9 2ohm 3 way open box on sonic electronics, $29. Sound deadening I bought 2 boxes at around $30 a box for noico and closed cell foam 2 boxes $20.