Best player for FLAC is Teclast T39 nowadays. Meizu M6 SP (haven't heard the SL) was quite OK but not even equally good as the iRiver ifp-799 loaded with 320kb/s mp3's. The Vibez sounds terrible to me - colorless, dull midrange, like in mediocre quality mp3's, and even the lossless formats won't help.
Another good solution is to buy iRiver E10 from ebay and rip all the music to ogg Vorbis q10 using aoTuV encoder. I can't distinguish it from lossless, while the regular Vorbis encoder isn't totally transparent. Sticking to the lossless is a bit misleading in portable media world because in most cases it's the hardware to create the SQ bottleneck, not the file format. Many lossless ready DAPs don't even reach the quality level of mp3 320kb/s.
You can also consider the vintage Rio Karma as very good sounding DAP. It's convertible to flash with a 32GB CompactFlash + adapter.