Lena,

To be honest, your amp is probably way too much for those little speakers. Depending on where you have them crossed over, they really probably can't handle much more than 100W, if even that. However, in a room that sized, and given the speaker's efficiency, I would actually be kind of surprised if they are giving you problems. Your ears should probably be bleeding before the speakers give up on you. However, if you really are cranking the system, some more robust speakers are probably in order.

Def Tech's non-powered towers are really quite good. Most of them are bi-polar, meaning they fire sound from the front and the back. It gives a more "diffuse" sound. For two channel music, it's kind of pleasant, although the imaging may not be quite as good. In any event, one of their dual-woofer 5-1/4" towers would probably get you stepped up for output and power handling.

I've never seen the crossover in a Def Tech speaker, but from their literature, it sounds like they actually give it some thought. Based on the independent frequency response measurements I've seen of their speakers, they are probably pretty well designed. So, despite making a "hasty" decision on your speakers, you picked a good brand. The unfortunate thing is that they probably weren't intended for such a monsterous amp! Down the road, if you decide to upgrade, atleast you should only have to do the mains, and maybe the center, if you don't feel it's up to par. The surrounds should be pretty close to being "voice matched", so I wouldn't think they would need to be upgraded. They don't normally see the same kind of power (at least not for very long durations) as the front speakers, so they will probably serve you fine.

Jason