I have the AudioEngine A5+ and just wanted to add my take on a good option. My wife just got me the SVS PB-1000 and I can say its a great performer. I'm using it in a 17x34 family room and its sufficient, though I don't go crazy on the volume.
One thing I like about the SVS PB-1000 (and the SB-1000) that SVS does not really advertise is the ability for the units to pass 80hz and up to powered monitors. I occasionally place the PB1000 in the AE A5+ system and the result is incredible. The A5+ do only the mids and highs while the PB-1000 takes the lower end. Carmen 270 referred to the AE 5+ variable preouts which is great but I think going at it the other way and having the AE A5+ doing less work makes for a better sound. At least it did in my room. I looked at HSU, GE, Def Tech, PSB, and lots of others but as far as I could tell no one else offers this feature. If you have quality powered or active monitors I suggest taking a look at these SVSs. Btw, it was great working w/ SVS.