I reviewed about 10 true surround-sound headphones for Computer Power User Magazine in November. Sometimes, i really have a great job. ;-)
The Turtle Beach's recommended unit (above) have the best overall sound, but they clamp on your head a little more tightly than any of the other units, and I found it uncomfortable over time. They don't reproduce the 3-d effect quite as nicely as the other two I'm about to mention, but they do music better, if you follow me. 3-d sound is very convincing, of course, but the others do it slightly better. TB make the best sounding USB headphones too.
The Speed-Link/Medusa's sound almost as good as the Turtle Beaches, but they reproduce 3-d sound better, and are much more comfortable. They also have a nice amplifier with lots of jacks for cross-connecting lots of equipment in and out. They are about as expensive as the Turtle Beach's.
The Tritton AX51's use basically the same body as the Medusa, but they trade a little subwoofer size for a rumble pack. They sound almost as good as the medusas and have better 3-d sound than the TB's. They are also a bargain. Check out
http://www.newegg.com/Product/Product.aspx?Item=N82E16826235003FWIW, I use the Medusa's for AH (and other games) every flight.
For more info, go to
http://www.computerpoweruser.com/ and read the archives (you might need to be a subscriber to read the whole thing - sorry.)
-Llama