If you're going to use two different headphones, you might as well keep the phoebus. The EssenceSTX doesn't support analog 7.1. As far as the difference in quality between the STX/Phoebus, I doubt it's much. Unless you're listening through $1000 headphones, you probably wouldn't be able to tell. The moddable opamps of the STX is nice, but the 7.1 tradeoff isn't, if I used 7.1, I'd rather have that than slightly different sound (it's hard to call the sound better, the opamps kind of just change the parameters of the music a bit). As for the headphones, I'm a sennheiser fan myself. 595's was probably one of the best purchases I ever made. I've been considering stepping up to HD800/700 but I heard they aren't as good for the music type I listen too. But then again, a lot of people said the 595's weren't either but I love them. If you like bass and are going for ~400 I'd look into Denon http://www.amazon.com/Denon-AHD2000-Performance-Over-Ear-Headphones/dp/B000MVEC0Q They are definitely bassy but they do everything else really well too. You're not going to get bass from senns. Don't get me wrong, senns will go low, but the AHD2000's are way heavier.