Are you playing them full range with bass heavy audio? IMO, these ones are a bit too small to be played full range, being sealed and all. Though they claim -3dB 57Hz, being sealed, they don't have any authority at their bottom end and really will be best crossed over with a sub, probably an 80Hz x-over. For their size though, they can handle quite a bit of power; bass heavy is not how I would describe them in my experience.
I am not saying they are one of the greatest speakers out there, but they certainly aren't bad speakers by any means.
You might want to consider a pair of Ascend
CBM-170SEs. Also quite small and very neutral sounding.