Yeah ive heard some bad things about the pro 900's mids and highs. Which is why i think the m100 is a better basshead instrument. How is the m100 unamped?
The only issue I've ever read on the Pro900 is shrill treble for some people. I did not experience that at all.
Other than that is pretty much stomps on an M100 from a basshead perspective. But, to each their own. If you don't want to try a Pro900 that's your choice.