I also have a pair of m200's that I've been very happy with. In fact, I just joined here to ask a question about them when I saw this thread right at the top. My problem is that I've had the speakers for two or three years now, and I've been thinking of adding a cheap subwoofer to extend their bass performance but I'm having trouble deciding how to do it.
I tinkered with the bass management on my audigy sound card, but it didn't seem to want to work (actually, for some reason, the computer crashed whenever I hooked a sub to the thing). I could just split the signal from the card and drive the sub, but I'd really like to crossover the output from the speakers so I can better integrate the sub. I'm having more trouble than I expected finding a cheap crossover, though. At least one that isn't meant for car audio, that is. I was also thinking of grabbing a cheap yamaha sub since they seem pretty reputable as far as price/performance is concerned. Cheap is the biggest issue here.
Anyway, I just thought I'd throw this up here and see what everyone's thoughts and recommendations are. Sorry if this is hijacking the thread, but it didn't seem too inappropriate to me. Thanks for any impressions.