Right now I currently own the ATH-M50's and XB500's. I'm looking for something that has detailed sound quality like the M50's, but they lack some bass(to me atleast). I got used to the bass on the XB500's and I'm a basshead, but I also love outstanding sound quality. So, maybe something similar to a combination of these two headphones. I've also been looking at the new Sony MDR 1's and the Denon D2000's, but I don't know if those have enough bass.
Oh, and maybe something with better highs than the M50's too.