Depends what you'll be using it for & in which OS. Older OSes & PCs might like the earlier version(s) better. Otherwise, definitely ver 9 over 6. Why? Try it out for yourself & see.
Apart from the usual ones like RealOne, Musicmatch Jukebox, Winamp, Quicktime there are other less known ones but very competent all the same. They are (to name a few & all freeware) - 1. Quintessential Player - click here, 2.dBpowerAMP Audio Player click here, 3. FooBar (small memory footprint) - click here, 4. Zoom Player - click here, 5. Sonique -click here.
Each individual prefers one over the other & depending on his/her needs. I'd suggest trying out a few to see which suits you best.