I currently use a pair of HFI-780s with an Astro MixAmp for movies and gaming, and I have to say, I love them for both. I was so loath to give up the HFI-780 for gaming when I was in XBL parties that I eventually picked up the Labtec mic and did a boom mic mod for the 780s (just used some self-stick velcro for attaching the boom mic, nothing intricate). It's worked out well. Still need to test it in some more in competitive FPS, though, to see if it works better or worse than the A40s I've been using for that. (Hey, I got the A40s and mixamp combo before I got into audio stuff. They aren't fantastic, but they do work fairly well for soundwhoring.) I have a suspicion that the bass might be somewhat distracting in multiplayer (plus, I'm not sure if the soundstage with the A40s or the 780s would be bigger. What do you guys use to test that?)
Anyway, another recommendation for Ultrasone+DH from me. If S-Logic and DH work for your ears, it's a great, fun combo.