I have a couple of these DAPs the first one since January. Have learnt a lot about them now and yes, without doubt, superb. Personally I find upsampling is not normally necessary providing good quality WAV files are used, 16/44 is perfectly good enough when extracted from my CDs. You can tell on this DAP that WAV is far better than FLAC. I got both of my machines from Amazon U.K. and have to say, the level of support I've received reminds me of what was the norm back in the late 70s and 80s.
I havn't yet tried the S/PDIF in but have used it into a separate DAC and then into my valve pre/power amp - stunning!