TicTacToe, I almost went with the Astro A-40, but didnt for a couple reasons.
First, the mixamp, while it looks nice, seems more geared towards xbox users rather than pc users. Game/Voice control doesnt work on PC since the soundcard itself controls all that and there are controls in software that can control volumes. Taken directly from the A40 Mixamp Guide pdf file
If you are using Voice Over IP (VOIP) software, you will not be able to adjust the voice/game balance using the BALANCE dial. Voice communication software and game sounds are mixed together at your PC, and you should make any adjustments within your software. The balance dial balances game sound with voice communication coming into the Daisy-chain connector only.
So unless I misinterpreted, it seems it will not work as intended since the PC hardware controls the volumes independently.
Second, The headphone itself, from what I hear is basically modeled after the Sennheiser HD555. I have heard pretty good things about the A40, but I have heard nothing but good things about the 555.
Third, after a little research, I found a great soundcard to use that has all dolby technologies built in, including dolby headphone. The Xonar D1 from Asus.
So I ended up getting the Xonar D1, and the Sennheiser 555. I came in at a cheaper price than the A40, have similar or better sound quality, and only sacrificed the microphone, which i already had a desktop mic (that is more than adequate for my purposes)
Dont take me wrong, I have no experience with the A40, and from everything I have heard, it sounds like a great set, it just didnt quite match my needs, mainly because the Game/Voice control doesnt seem to apply for PC users and I already have a desktop mic that for my purposes is more than adequate.
I got my soundcard and Senn 555's this morning and tested them out. So far, the headphones sound great, even though I have read that with some burn in time they will sound even better. And I loaded up some games using dolby headphone, and yes, it really does work. I didnt quite think it was possible, but out of a stereo headphone, but I can hear sounds coming from all sides, and even behind me. So I would say that I am glad I steered away from 5.1 headphones because now I have a better set of headphones that can be used for stereo and I still very convincing surround effects.