What would be the best 15" subwoofer for a Kenwood amp (550X1 @2 ohms). SPL/SQ 60/40. I was looking at either a CVR15 or an Avalanche 15. Trying to keep the price down as much as possible so in the range of those. Any suggestions? Probably going to port the box and give it about 4 cubic feet tuned to 28-32Hz depending on the sub.