Subs do more than provide deep bass. They enlarge the sound stage.
I use a SVS 2039 PC Plus, a powered sub. It's a tall cylinder with down firing woofer. Recently I laid the woofer on it's side and was blown away. I bought a n oversized creeper from Harbor Freight http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=2745 ($29.95) which not only holds it nicely, but has 6 wheels, so moving it around to experiment is easy. I find a bit of tilt to improve the soundstage. THe head rest helps this. I tried various locations- sideways firing in/out, then front to back firing front/then into the listening area. Front wall is 10 feet of glass and rattles like crazy at 40-50 hz, let alone deeper, so I am firing into the listening area.
Also I am biamping with a Behrnger CX 2310 XO