Thanks for all the replies, as for amplification of the 650, from what i've read and heard, people encourage amplification with the hd 650's, but say they arent as power hungry as other high impedance headphones. Which is why im going with sort of a starter grade amp, which can power my other headphones as well (not getting this setup purely for the sennheisers) Im going to try out the asgard which is a solid state amp, then perhaps move on to a tube amp and try other headphones later.
Really a huge factor in me getting the HD 650's are comfort and of course sound. Someone mentioned HD 600's which i looked at, but every review i read says the 650 has noticeably better bass in all ranges and although im not getting these for bass (I have other headphones for that).. More still means better so that is why i chose 650's.
-Keep in mind i will be wearing these many hours a day.-
The only real issue im worrying about right now is, because they are open back, im wondering if the mxl ac404 desktop mic im getting will pick up the background noise of the headphones. The mic is made for voice and is suppose to block out everything else, so hopefully it does just that.