I am confused why are the 780 cheaper than the 777 model? Isn't the 780 the better model of the two?
I am going to take a guess, I think it's probably because the sound card etc are built into the headset, so that cuts down on the additional cost of having a sound card that you plug your headset into and then the sound card into the PC. Or as above it could just be an introduction offer.
I am Polyninja's friend who got a pair of 780's with the loose volume control, getting a replacement pair next week (sorry guys got them elsewhere before you dropped the price).
Apart from that issue i can say the headset is very good and of excellent build quality. I was previously using an X-Fi Xtreme Gamer and CMSS-3D and can report that the surround sound is much much better, I always had a hard time knowing where people/sounds were coming from on the CMSS-3D especially if it was behind me. No such issue with this set, though the jerking your view round to the sound automatically does take a little getting used to.
Movie wise the surround sound seems to perform fine at 5.1, I don't have any 7.1 movies to try.
The mic is very very clear, however I do wish the noise-cancelling aspect was a little better as you can hear my TV through it and it picks up the fans etc on the computer (not sure how other people are finding that, it could be something else faulty with my current set, will update once I get a replacement).
My only other minor gripe is the length of the cable, I am going to have to grab myself a USB extension cable i think as I very oddly keep my PC on my right hand side rather than left. Though that's totally my fault as it would not be an issue if my case was on the left.
But I can highly recommend them, good sound, good build quality and the fact I am getting a replacement rather than a refund suggests I must be impressed.
I'm not an audiophile but I would give the sound: 9.5/10
Build Quality: 7/10 (Taking into account the loose volume control will update when I get a replacement.)