The MMX330 is a rebadged DT770. Plenty of reviews to read up on there if you do a search. I would consider the bass on the DT770 to be a little too much for competitive FPS gaming, but for casual gaming it should be fine.
As far as I'm aware, the PC350 is based on the HD380 which I quite liked.
My main concern about the PC350 is a. the build quality, since i'll have to wear them for 9 hours a day minimum.. b. the sound quality with music (i've read about poor basses and muddy sound overall)
About the MMX300... i've read something about DT770, i'm not much worried about the bassy sound, since i'm not a fully competitive gamer, and i can use some EQ, plus that SHOULD be a pro when listening to electro, ambient, minimal and stuff. But im more concerned about the lack of mids and the "muddyness" (lol) of midbasses... can you confirm this?
Thanks thanks thanks for your replies :)