If you have the HD280's ...they SUCK. OK for tracking but pretty useless for mixing. Senns higher end line stuff is pretty awesome. I had the old HD580's and they were outstanding. I'm a die-hard Sony / Senn fan when it comes to phones... BUT, I've never tried the ATH-M40/50 so going to get the 50's ...just cuz.

7509's... all of the above. I've had them forever and the drivers are starting to become 'weird' sounding... I know, not very descriptive but they have changed.