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
I'm using a pair of Shelby+Kroll monitors and matching S+K subs. I found the Dapeaker Dual Core 2.0 to be very helpful in taming room nodes. The bass sounds awesome and by clearing it up the highs and mids significantly improved. 
I just added a svs 12" sub (sealed) to my pair of rega rs5.  Crossover set between 60 and 90hz on the sub depending on my mood, no cut-off on the regas.
very enjoyable, i may add a 2nd one later.  I used to have vandersteen 2s sig, but now, i can customize the output.
i have always been reticent about using a sub because i thought good integration could be difficult to achieve.  Well, This was a false belief.  I actually may actually switch to true high-end bookshelves at som point.
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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.