One Sub or Two?

DCM. NAD. KEF. JBL. Do you recognize these acronyms? If you do then you'll probably recognize the names McIntosh, Revox, Carver and at some point in your life, you spent a pile of money on stereo equipment.  Well I still have my components from over 15 years ago. A Soundcraftsmen pre-amp, NAD amp, and a pair of Infinity 3way speakers. It's about time for me to get some new speakers so I started twiddling around the net to see what I could find. Nothing yet, but I did find this, an interview with the legendary Bob Carver. I'm an audiophile from way back in the day but it has been a long time since I've put any serious money into my system. I bought a couple studio monitors for my computer a couple years ago - a pair of Resolv 65a. They're great, and I listen to mostly AAC encoded music at 320kbps which is really good enough. But now I've got the beginnings of a new itch.  For a subwoofer. Just one, that's all I need. Or is it?