So how many people are using subwoofers

Karls is dead-on and I also have to second Glen's opinion on the MITs. The REL blends seamlessly with the few speakers I've heard it with (I use Thiels) and it really is true that you have no idea what you're missing until you hear it. My Strata III (great for a 13' x 17' room) did crossover best almost on top of the Thiel's low boundary but that seems to be the rarest configuration.

upgrade the amp, it will benefit the whole range, not just the lower end.

I just went and saw the Buggtussel factory. They have a subwoofer the Tegmentum 12. I heard this subwoofer powered by their own amplifier and processor unit. I listened to it with the Amygdala's and the Solitarious speakers that Buggtussel also makes. All I can say is I was very impressed. The sub was very musical and very powerful. It blended seamlessly with the other speakers, and coupled well with the room. Something to look at if you are in the market for a subwoofer. I know I am looking to add one soon :)

I'm having good results with Sunfire subwoofers. I know Bob Carver is controversial and often disparaged in the high end community, but his engineering is sound. His True Subs are tight, fast, and go low enough for me. I have a pair of True Sub Signatures supplementing a pair of WATT/Puppy 6s well in the low bass. I have a True Sub Mark II under a pair of Red Rose R3s, and the sub works in the low to mid bass. For this location, it sounds better than the REL Strata Mark II that it replaced. I have a True Sub Junior working with a pair of Proac 1 SCs, and this is effective in the mid bass but not really in the low bass. (The Proacs are in an installation that would not accomodate a sub bigger than the Juniors.) The fact that all these subs are as small as they are is important to the rooms where they are located.

Very interesting read, here. I had a storm3 it did wonders for my Aerial 10s. When I changed to Montana ESPs I never liked what the sub was doing;and sold it. I certainly concur; bass improvement is found in ALL the components that make up your system.--For me it was more the "tone" of the bass that mattered most to me. I have read threads by people whom have 6 subs.So, yes, we have our special,but different priorities. Tone of bass being mine.