Thanks to this thread, I pulled the trigger on some HD 580's I found on kijiji for $80. So far really liking them (no amp, using headphone out on my Outlaw RR2150). I have already boxed up my HD518's I just bought so I can return them (they weren't bad, but trying to have only one headphone of a particular type).
The earpads are pretty worn though. The seller did a DIY re-foam (I wonder if he got the idea from Head-Fi) but the actual velor material looks pretty rough. Was thinking of getting the earpads for $30 from eBay (Hong Kong seller)... has anyone gone that route?