Koss and Sennheiser should be good. It you are on a budget buy Koss, if you want to burn some money buy Sennheiser. although Sennheiser are alot cheaper then they used to be! Grado is an old company like both of the others, so Grado might be fine. Grado, used to make great products. I bought some of their cartidges for a turntable.
Besides sound the most important thing is to get ones that are comfortable. Get the kind that enclose your ear, (like you said) not just sit on top of them. They are bulky but have the most comfort, like the ones you would see in a recording studio. They are called the close type headsets.
You probably cant go wrong with either, but the Koss are great quaility for the price. I have an old pair of Koss and Sennheiser, the Sennheiser's cost me a ton 10 years ago, my Koss didn't and both sound great.
I checked out the Grado's they got great reviews, only problem I see is that all of the headphones are open air, meaning they don't enclose the ear. The problem with open ear is the fact the sounds from outside the headphones can be heard. I find open air less comfortable, I havent tried the Grado's though.
That all said, either should be fine. Availablity might be a problem. Koss and Grado are USA companies, Sennheiser is German. Like most sound products you need to listen to them for awhile and see what sound best and have the most comfort.
I like the Pro series for Koss, my Sennheisers are no longer avaialbe in my model. here is a link to Grado model 60s <A HREF="http
/www.gradolabs.com/frameset_main.htm" target="_new">http
/www.gradolabs.com/frameset_main.htm</A> You may have to check out an independent high end streo type store to find these to listen too.
Happy searching,
the Prisoner
I'm not a number, I'm a free man!