I owned a Fiio E9 when I had the Hd650's, and it powered them just fine, but the E9 did'nt make the hd650 any more energetic than it could be and not exciting as some may wish, but this is the 650's were talking about which is already a laid back Headphone - Imo the Hd600's are more geared towards Dance Music. When I owned the E9 i remember wanting to upgrade to a better amp but I figure that I just didn't like the sound signature too much - being a dance music fan - like yourself, the 650's didn't provide the bass kick I craved, but for soundtracks and classical tracks the Fiio E9 did the Job well enough and provided equal volume across the spectrum. I never did upgrade the amp so I can't speak much of "better amps" for the 650's. I now I own Hifiman he-500's, the Bass impactfulness I craved is there. I suppose it all depends whether or not you want to add color to the sound signature, and from what I recall the Fiio E9 is a neutral Solid State amp. Maybe try looking at a tube amp if you want to warm up the sound, but if you're after more speed for Electronic music maybe change the Headphones?
Edited by fluidz - 10/27/13 at 7:13pm