We've had good success with a REL Strata III hooked up to Threshold T-200s (simple stereo setup, not home theatre as you have) in a 15 by 18 listening room. Adds a nice bit of "thump" from many CD Jazz recordings and most DVD movies, but otherwise stays out of Avalon Eclipse's way. Easy to adjust as well.
Avalon Eclipse's..To Sub or not to Sub
I currenlty own a pair of Avalon Eclipse's and have been very happy with them for the past 5 years. However, when I bought a decent sub-woofer for my Home Theater set up I was impressed. Does anyone have any experience adding a sub -woofer and what kind and make to these Avalon's.