I agree with Mark that open is the way to go. IMO theyíre much more natural sounding and you donít get that pressurized feeling during loud passages like when your ear is totally enclosed. However, one drawback to open is that they donít attenuate outside noise so they work best in a quiet area. This is also an advantage if you need to hear the doorbell/phone ring or are just paranoid like me and donít want anyone sneaking up on you.
You could also look at Sennheiser: http://www.sennheiserusa.com/newsite/category.asp?transid=cat0
I liked the sound of the Grados but canít stand wearing on ear headphones so they were a no-go.
I have the Sennheiser HD600 but these are similar but maybe a little above your price range.http://www.sennheiserusa.com/newsite/productdetail.asp?transid=newHD-3
Iíve worn mine for over 16 hours without even noticing they are there. The felt pads allow me to wear reading glasses with no discomfort. On several occasions Iíve had the headphones yanked from my head when I walked off forgetting I had them on.
One problem for some of the Sennheisers is their high impedance causing them not to work well with portable devices unless using a separate amp. However, mine work just fine with my Denon 2807 receiver. I donít think any of the Grados have impedance issues.