Hi. I don´t know if you want one more opinion, but I´l tell you mine, cause I have both, in diferent rooms of course. The results always depend to the electronics you´re matching to these speakers, OK! I have the DM303 since 2005 hooked to a Harman Kardon AVR 435 and they sound very well, but for stereo you need to use a subwoofer, otherwise DM303 won´t handle bass satisfictorily. I think these speakers are a gem in hifi world, considering the price. Then in 2008 I bought a receiver Denon AVR3808Ci and the 685. In the begining, I thought I made a big mistake, but after two months, I could feel how this "pair" gave me what I was expecting from them. For me, I don´t need a subwoofer for stereo cause 685 handles bass enough and the sound is much calmer for me. I think the principal diference you´ll feel, if you make the trade between DM303 x 685, considering the size of your room , it will be a more calm and refined sound with more punch than you have today, and probably, you won´t need the sub. Only if you like bass a lot, then keep it. I hope I could help you.