Bob045:
I have the same receiver and am doing the same thing except I have M200s across the 3 fronts. To adjust the levels of the speakers simply hit the test tone in setup, you can then adjust the levels of the center and rears to match the levels of the front L&R. You will find that the M200s make a remarkable improvement in the sound and is especially evident in the bass output of your speakers as compared to the Yamaha. Bass seems more "punchy" (hows that for an audiophile term ;-). I am very happy with my 200s.