I just replaced stock door speakers in my old-but-new-to-me surb and the improvement was stupendous. Next is the stock subwoofer. All it seems to do is add a kind of very low boom, but it's mushy, loose, "low" sounding. For simplicity I'd like to keep the amp if at all possible (it had been my experience that upgrading stock speakers has greater yields than electronics upgrades). I'd also like to keep the stock enclosure, no box in the back. Does anybody have recommendations for improvement? Specific drop-in upgrades? And can anything be done for the factory EQ except swap out the amp? I'd to dial in a warmer sound (mid-bass), less low end boom. Thanks in advance for comments!