You really don't need FLAC files for hi-fi.
320Kbps Mp3 files will give you indistinguishable sound; however, if you're skeptical, there are various tests you can take online that will disillusion you of the notion.
That said, it's possible that a good DAP can give you superior sound, if for no other reason than they have a better amplifier with more power, which will give you 1) Better volume and 2) no distortion on devices that need a lot of juice to run properly.
The Surfans is a perfect "entry" device, and frankly, unless you just want more features, it'll do the job for even experienced audiophiles. It will also play nearly every audio format, so if you still want FLAC, you will get it.
The Surfans has a 100-step volume control, and is one of the few DAPs remaining with dedicated tactile buttons for all functions. It doesn't even have a touch-screen at all!