Headphones for Rogue Cronus Magnum

Good afternoon. I'm starting to get a bit confused by all the choices in full sized headphones. I think this is because so many people use them with ipods etc. I'm looking for some headphones that would run about $300. I would be using them with a Rogue Audio Cronus Magnum integrated tube amplifier that puts out 90 watts.

I've got a fairly large head. Listening for 2 hours at a time would not be out of the question. I listen to jazz, a lot of it with vocals such as Cassandra Wilson. I also listen to blue grass, some folk and a little rock and roll.

I was serioulsy interested in the Grado 325si, but am concerned that I would get fatigued from the highs and also that they would be uncomfortable. I like the Sennheiser SD600's but they take some power to drive them which I guess I have. AKG's sound like they might be nice but that's a heck of a break in time and I don't want to put my tubes through 300 hours of use to break them in.

Any advice would be greatly appreciated.
The AKGs sound good right away. The break in, of course takes place, but while you wait, the sound is still very transparent and loverly IMO.
BTW see if you can find 701s. They should be within your budget. They are last year's model and more, they been around awhile. No longer TOTL but super.
I found the AKG K702's for $248 new. That seems like a pretty good deal.
I ended up purchasing the AKG K702's. I'm glad I bought them when I did, because the price started to climb back up. I got them for $248 and now they're at $259. Everyone else sells them for $399. I feel bad for anyone that pays that much for them, so if you're looking for these particular headphone, buy them from BH Photo. That where I've purchased all my camera gear/lenses. Their getting big into pro audio gear.