I've had experience with Fiio, Shanling, & AGPtek. All three brands were serviceable. The AGPtek being the cheapest @ $69 USD, however the AGPtek model (which I
would recommend) is unavailable at this time.
I’ve borrowed someone’s clip ages back, I’d forgotten that. It does work with the Mac just fine. I think that might be what I get.
As far as I know, they don't make the Clip anymore. DAP's are a niche product now, so if you want a good one with a solid UI, you either pay for one from the established DAP makers or you research into something with the features you want. This
HeadFi thread is a good resource.
I posted about the Clip killer in the
audiophile thread, the
Shanling M0, but it may be out of your price range.
It has a tiny touchscreen and only one button, but works well with gestures etc. Check out
Penon Audio and find something with features you like, then check amazon.uk for the product. Both Shenzhen & Penon Audio ship worldwide and are trusted by the ChiFi audiophile scene, but I understand why amazon or something would be better for most people.
This
Ruizu M4 might do the trick for you.
Ruizu software has a bad reputation, as
most ChiFi DAP's do, but for less than $30 USD it's probably worth giving it a shot. I don't see any reviews on that particular DAP, but the slightly more expensive
Ruizu A58 has a poor reputation for audio quality.
Mp3tag can be used to repair metadata. Don't know if this helps any.
MusicBrainz Picard is cross-platform and uses fingerprinting to identify audio. It is top notch free & open source software.