So far so good
I've been "working" with the A40s (with Mixamp) so far and I have to say, I've been very impressed. Since the X41s and Trittons haven't come yet, I can't compare sound quality, but the Astro guys clearly paid a lot of attention to the details of their product. The balance knob on the Mixamp (balances voice and game audio) is a very nice touch.
Granted, the A40s are cabled, which is a serious drawback (especially depending on the configuration of your living room), and they are a little more pricey than their competitors. But so far I've found these to be pretty comfortable and solid, and they've helped me basically lose all interest in going back to a traditional surround speaker setup for gaming.
I myself am also looking for a definitive yes or no to this, in which case I will most likely buy myself some good quality headphones, get a clip on mic and get my Sound Card in my PC to create the virtal 3d (which currently sounds great on my Etymotics).
Both have pros and cons though. The clip on microphone is not going to be as good as the A40 microphone plus you might have to be shouting to be heard, plus you've also got to deal with that cable however you have an awesome pair of cans.
With the A40s you don't want to be listening to music on them but they are the all in one device for games.
Its too bad that I can't listen to a demo pair in Australia, I'm just going on the specificatons of the A40 headset.
I don't think you can discount how much a difference big speakers make for sound quality. Music sounds a lot better than any earbuds I've ever used. I haven't tried many other over-the-ear headphones, though.
If you just use the headphones, they are a normal set of headphones with a mic. I used them once as a headset to talk on my Palm Pre.
With the MixAmp, you can enable or disable the Dolby 5.1 by hitting a button in the lower right. I disable 5.1 when I'm watching TV programs that don't have a 5.1 signal. If I'm listening to music, I usually don't bother with the MixAmp, and just plug in the headphones directly.
BTW, I did notice a huge difference in sound quality, depending on how the MixAmp is powered. I originally used the USB hub that was included with Rock Band, and there was a lot of background noise when the sound from the game or TV was relatively quiet. I thought it was the MixAmp, and was annoyed that I was going to have to get more batteries. On a whim, I decided to plug the USB cable into the back of my DVR instead. Now it's quiet and has really good sound. I suspect that the USB hub that came with Rock Band is relatively cheap, so I figure that's why there's a lot of extra noise.
Hope this helps.