The difference between the m/m combo and the fiio combo is pretty stark. The fiio is warm and laid back while the m/m does sound a little bright to my ears. The brightness is coming from the modi though. Just compared them this weekend.
If you're looking to "brighten up" your 650 the m/m would be something to consider. I don't feel the need to brighten mine at all.
Edited by MattTCG - 2/11/13 at 4:38am