You can trust Apos, here is their return policy:
http://help.apos.audio/en/articles/3076135-apos-audio-30-day-return-policy
They are somewhat active on the forums here as well. (at least, they are watching threads for products they sell)
I have no experience doing returns with them, but their communication is top notch and I have no reason to doubt their policies.
I would definitely buy from Apos, as I'd much rather support them than Amazon as well.
From what I can tell, Apos is just as US subsidiary of Shenzhen Audio, which is who I normally purchase from anyway.
Even when ordering from Apos, my DAC shipped from Shenzhen Audio in China anyway lol, but it did so with 2 day worldwide DHL!
Shenzhen Audio has been a dream to deal with, and they even have an active
Discord server (probably an expired link, you can ask me or them for a new link) for their customers to chat in that has both English and Chinese customer service!!!!
Also keep in mind that on Amazon, you're often dealing with third party sellers for this kind of stuff, though they try their best to keep their high ratings so you probably won't have issues with either company. Just make sure you keep all packaging and materials and return it in the same condition you received it and you'll be fine.