I have been using (and still do) Grado phones for about 6 years now and love them. I recently purchased a 600ohm DT 880 600 and they are quite good for rock, just last night I was listening to 10 000 Days by Tool with them. I actually like the fact that the DT 880 steps the mids and treble back just a little as it helps make all those horendously compressed rock recordings bareable!
Shame you don't find the Grado's comfy enough for you, but for sure the DT 880 is comfy. I use a Valhalla amp with my cans as well as a solid state amp and both ways are great. The Valhalla provides a more forward presentation of mids and I found listening with the HF2 and aggressive rock sometimes too forward in the mids, not very much so, but enough that I would turn the volume down a tad. The 880 and the Valhalla don't suffer this due to the slightly recessed mids.
I love Grado, but if you are going tube and really like rock you might find the 880 a compelling fit. From what I read the 600ohm version sounds the best, but if you go that route remember your amp must be up to the challenge of driving the cans, and forget doing it right from an iPod without an amp to assist it. If you are buying for mostly home use then really give the DT 880 some consideration. If you aren't completely against the Grado feel then try to get either a used HF2 or a 225i. Cheers.
