I'm not a Sennheiser man, but I would think it would be an excellent match.
The Headphone out doesn't sound all that great with high impedance headphones... better for Grado's and the like. The XLR outputs are another story.
Male is the standard though, so it might be better for you to get them terminated that way and get some adapters or have adapter cables made... I'm looking at making some cables anyways since I don't want to have the Lavry in my rack backwards all the time.
I like the E4's quite a bit... certainly better than the HD201's [which I own] and the A900's [which I hate]. But when all is said and done there isn't a chance in hell I would listen to them at home with the K340's and HF-1's around.
Yeah, it should be fun... I'll just have to try to stay away from the beer until it gets later. I don't want to start... I don't know... rubbing someone's lambskin headphone stand or something. Not saying that has happened before or anything.