Josh, I think Keith has it right: Go for a pair that covers your ears snugly, and sits comfortably yet snugly.
I've got a pair of Sennheiser HD 25s which I use with my PD150 and a Shure FP33 mixer unit. I've found them very rugged, very dependable, good in high ambient noise situations, and comfortable to wear for extended periods of time (which is saying a lot in North Indian summer conditions - 42 to 47 celsius May through June!)
And, oh, the sound quality is simply fabulous - it's a pleasure to use them with agood mic lic the Sennheiser 416!
My two bits...
Ram

Sounds good. What are we lookin' at money wise here?

Ooh, now you've aked the dangerous question! :-)
I think the HD-25 is available for about US$250 (need to check on this - while I try to get more accurate figures, you could ask your local distributor. You can get a name and contact details, as well as more info at http://www.sennheiser.com/sennheiser/icm_eng.nsf/root/products_headphones_professionals_02976?Open&row=7
(this is the link to the HD-25 page on the Sennheiser site)
There is a lower cost version of this headphone availabel called the HD-25SP...but I wasn't very happy with it. That one's for about US$100 - 125.
They do have several other headphones - even if you are on a budget, I'd recommend you try out some Sennheisers. I've been using them for a long time, and they've never given me trouble.
Hope this helps!
Ram