I play through IEM's live (and when I practice) and I quite enjoy it. In fact I prefer it to my studio monitors in many ways. There is no room to colour the sound.
I tried the headphone output on my AxeFX II the other day and I found it quite a bit different than either the mixer in my home studio or the mixer I use live. I suggest you try a different headphone amp to at least see if the one in the AxeFX II, in combination with your headphones, is colouring the sound in a way that is not complimentary.
Terry.
Terry - really interesting; I've heard the same from a friend as well....may I ask what IEM's did you decide on and can you recommend the best setup/config for them? Thanks