My point isn't to look for budget headphones, it's to get the best bang for buck in the higher end headphones. Those Onkyo's being on ear rules them out, I didn't realize that. I'm pretty positive on the M-100's right now.
I have some Sennheiser HD428 that I use for recording and mixing, maybe those are more flat response than the M-100's. M-100's will be more enjoyable for music for sure.