So far, yes I do like them, very much. I haven't quantified them completely, except that they are very good, and when you factor in price then they are amazing! They work startlingly well with virtual surround FPS gaming, but I want to hear them with more of my music and maybe a movie...
I don't have the wired Mixamp, but on the Mixamp 5.8 the K612 dampens the hiss slightly more so it's slightly quieter than my Q's, but it's still not as powerful or clean as a discrete amp. Like gaming at 1080p resolution, but low graphics settings. The DSS has a bit less hiss, but still... amping improves soundstage, separation, and authority to the bottom end. You might be happy enough just for gaming, but an amp just makes things nicer.
A firmware update got rid of popping issues I was having, but I still haven't gotten my optical out working.