I have Grado SR-80 headphones, some old Yamaha ones, Sony earphones, and Shure SCL3 earphones.
I had an OmegaStar preamp for a number of years and have since had it updated to the Insight series.
It has always done very well on headphones, and driven everything I've hooked up to it.
The Grado SR-80 is very good, although I think the Shure SCL3 sounds better. Not everyone likes the in-the-ear type of 'phones though, so the Grados might work better since they're on-the-ear.
My brother has a pair of AKG K240 headphones. They sound decent and are very comfortable.
A friend has the Sony MDR-V900HD headphones and really likes them. I haven't heard them though.