I've decided to purchase a couple of subwoofers for one of my 2-channel systems and I'm open to suggestions/advice. Music only, no HT. I'm limited on space and need to keep the size down to around 15" X 15" floor space. So far, I am considering the Sunfire HRS series, Elemental Designs A3S with 2-band parametric eq, and Definitive Technology Supercube II. I would also consider an SV Sound cylinder sub, but due to size I could only use one of those. A Hi-Fi dealer that I have been dealing with for over 30 years strongly recommends the Definitive Technology and uses these in his personal system with Magnepans. In general, I've always prefered the sound of subwoofers with passive radiators, but I'm open to other designs as well.