need subwoofer for HTS 50 music,50 movies

after trying diferent speakers(in sealing speakercraft,kef....)i desided to go with Sunfire brand,the front two are CRS-3(250 w RMS),center CRW-3C(250W RMS) and two backs CRM-2BIP(250W RMS),and right now i am testing them with Sunfire HRS-12 sub,runing them all with DENON 3312,sound is incredible,very clean,loud and no distortion ,the only piece i am completely not happy with is the sub ,it has very deep and continus base whitch is great but when it comes to speed,tightnes and midbase response is not there,terrible for music,ok for movies,room size is aproximetly 2500 cubic feet,looking for similar size as sunfire sub(14-14-14)or smaller.budget is around $2000