What kind of headphones would this dac/amp be good for? I am currently using a Sound Blaster X G5, would this unit be a substantial upgrade for me? No issues driving my headphones I have but I would be interested to know if sound quality would be night and day in difference. I few of the phones I have are the AudioQuest Nighthawk, AKG K7XX, K550, ATH-900x and V-Moda Crossfade M100's.