Personally bro I love them. I almost got the A40's (Plan on getting them one day) but I picked up the A30's since I could use it with my iPod, Phone and also use it for gaming.
As you might know know the A30's have more bass while the A40's have more treble and mids i think it is? Lol.
The A30's are built extremely well, Feel very sturdy and are.
I'd say the A30's are built for more for on the go stuff like iPods and such, but also being able to use as a gaming headset.
While the A40's are purely for gaming. I'd give a better comparison but since I don't own the A40's so I really can't say much.
But I can say they both are very very high quality products, I might they must be sponsored by the MLG for a reason. Hahah.
The MixAmp is really badass, I like being able to mix the voice chat with the game volume and also use it on my computer.
I can't say any faults on them bro, They work great, they look great, what else can I say, hah.
BTW: If you do get them make sure to pick up the rechargeable battery for the MixAmp, that way the only wire you gotta run is the digital cable, and just charge it up when your not using it.
Also, the digital/optical cable whatever its called they sell is really high quality, not just some cheap one. Just a heads up.