Definitely. Most of my music is 320 kbps and it sounds fantastic on my hd 650. I think there's even been studies showing that the majority of people cannot tell the difference between 320 kbps MP3's and lossless files like FLAC. Your mileage will vary though, everyone is different. Regardless, you should have no problem enjoying your MP3's on the HD 650 :)
+1. I've done some A/B blind testing on Foobar with 320 kbps ripped from FLACs... the difference is audible through my rig... but is honestly subtle. I have to actually be listening very carefully and using direct A/B. If it was just casual listening I doubt anyone would notice.
Thanks a lot folks! Yeah, I am no 'true' audiophile and frankly will probably never notice the difference, as long as I do not need to convert my entire library to FLAC or similar to get the most out of the HD650s, that was my primary concern. Now I really cannot wait for them to get to my house next week! :D