I had just received these headphones as an early Christmas present. I thought I'd be getting the new Koss studio series models of either the R/80 or R/90, but since the PRO486 is part of their older models, I got it on sale. It's worth about twice what the other two models are (in sound and price) too.
I have to say this is one of the best pair of headphones I have listened to. It is the first pair of studio-quality headphones I have owned, but I have listened to other and quite like these ones. They have a great, full dynamic range (Koss rates it at 10HZ-22,000kHz), and 100db/w rating. I'd give these excellent headphones a rating of 5, but I'm still thinking that there may be something better out there, for the same price, from a company that I probably don't know about cause there's no dealer where I live...

But since this is an older model and most places might be trying to liquidate it, I'll give it a 5 anyhow!