Hey, well I finally signed up to Head-fi. Guess your reply made me finally cut the rope. I've got a DT990 250Ω and a Musical Fidelity X-Can V8P as a set up. Hooked up to it is a HRT Microstreamer. I got the beyer first and then the V8P to match with it, because I think it does a great job in emphasizing the somewhat tame mids in the DT990. I can't really speak for the AKG but I've noticed on Sennheisers (HD 6X0's) and some Grado's (up to Sr325) that this amplifier has a very nice way of producing a 'Juicy' mids region. By juicy I mean the mids are there, defined, but lush, definitely not choking the other frequency areas.
Anyways, I hope to have given you something to work with here, good luck!
PS: I highly recommend to try out the DT990 with the microstreamer!