I have a pair of speakers in which the woofers are in separate enclosures (mid and tweeter is in a smaller satellite enclosure). The enclosure for the woofers are around 38" tall by 11" deep by 22" wide. They contain a simple 12" woofer and I'm looking for suggestions for upgrading the woofer for deeper lows and overall better quality at a reasonable price. The enclosures are 3/4" MDF. Any suggestions greatly appreciated.