I've had my M4's for about 6 weeks. They sound terrific in my small and difficult room (10' x10'). I have an ACI subwoofer available but, so far, haven't felt the need to hook it up. I'd say if you have a largish room go with the M3's. If not, the M4's will do the trick. They will play quite loudly and the bass is so clean and accurate you may not miss the slight bottom end extension. The highs will be the same since they are identical above 800 Hz but the larger woofers in the M3's will move a bit more air. There are great reviews out there on both models.
