So how many people are using subwoofers


with full range floorstanders? I need just a little more bass weight out of my system and have vascilated between REL subwoofer or upgrading my amp from Conrad Johnson MF-2200 to an MF-2500. 60-70% of the music doesn't need a sub,but that other 30% keeps me off balance. Is the amp upgrade going to give me more bass weight (along with other benefits) or should I just go for the sub? I think I know the answer but would like to hear other opinions.
existing system=
CJ PFR pre
CJ MF-2200 amp
Theta Miles cdp
Silverline Sonata speakers
Homegrown silver lace ic's
MIT-2 bi-wire
128x128artemus_5
Post removed 
Look into the Audiokinesis SWARM subwoofer system.  Four passive subs that you ASYMMETRICALLY distribute around the room with a 1000W amplifier to drive them.  No single sub, (even Vandersteen or REL), can compete with this system, if set up right, and its relatively inexpensive - about $2500.00 for the whole deal.  

Also see Robert Greene's review in TAS from last summer.  He said it was the BEST bass he has ever heard, (and he's heard it all).  I am using it in a Vandersteen 5.1 set-up and I can vouch for REG's observations.  It KILLS my single V2W.

to add to the excellent subs already mentioned here (Rythmik, SVS, Audiokinesis, etc) i will also suggest Seaton Sound.  i recently added a seaton submersive f2 and am EXTREMELY impressed with it's performance for music (for movies, a distant second consideration for me, it's staggeringly good).  for reference, i've also owned subs from JL Audio, Vandersteen and SVS and prefer the seaton sub to all others.
The Swarm system just seems cool and inexpensive…if I wasn't happy with my RELs I'd seriously consider those things. It's true that a lot of music doesn't get to sub territory, but I like the ambient aspect of the sub adding that airy reality to the mix a much as the direct bass reproduction...systems need that to seem more like natural sound.