Personally, I think it was raising the speakers off of the ground that made the most difference in my listening ... I tend to watch TV or listen to music while slouched down in the couch or chair, so the tweeters were already at about ear level.
I know what you mean about a room not being suited to an HT ... my great room certainly isn't (1/2 kitchen, 1/2 living room, all vaulted ceiling & *two* full sliders worth of glass on the back wall). Which is why I just run stereo up there.
I think you'll be very happy with the M200's and your Rockets.
As for modding them, I've never considered it ... I just can't see spending the money when I've been so happy with them as they are. I'd recommend using them stock for a while (weeks or months) and then consider modding them if you find them lacking. Just my two cents.
Enjoy!