The Beyerdynamic ear-pads fit the Sennheiser HD 280 Pros well, but a little stretching is required. The pair I ordered came with a foam/cloth pad to go between the headphones and ears, addressing a concern I saw in another post about having to add fabric.
After wearing the HD280 Pros with the DT250 pads for a few hours continuously, I've found one draw back. The DT250 pads are thinner than the HD 280 pads so the speaker does touch my ear. I'm considering adding a layer of foam between the ear pads and the head-phones to give a bit more space, but I'm not yet sure it is worth the effort.
As for compromising the sound, I can't compare side-by-side. I did the mod when the original pads had started to fall apart and I threw them away before I considered doing a comparison. That being said, if there is a difference, it is fairly minimal. I've read of a "blu-tack" mod for the Hd 280 Pros that apparently add bass, so if loss of bass with the pad-mod is an issue that bothers me, I'll give that a shot.
Oh, and while I like good sound, I do not think I have the sensitivity to be an audiophile. So take my input with that in mind.