nightday000I'd (probably) recommend the FiiO M11. I've only owned the M11 for about a month now. It has just under 512gb of music on it (FiiO states it will hold two cards with up to 2TB). I'm not sure the M7 is quite as good based on the single DAC but the sound on my DAP is phenomenal. I use it on a Bewitch tube (K88's) amp and a pair of Audio Nirvana 2.8 Mk II Ambience speakers as well as Monoprice M1060 Over Ear Open Back Planars.
The only issue I've had is that the learning curve has been steep. The UI is not as intuitive as I would like and loading new music can be a challenge but having two modern DACs is far superior than the 5th gen iPod Classic w/ the Wolfson DAC is was using before. The sound quality is worth the hassle.