Notes from my little bit of recent research into software audio players:
Vox is not intended for audiophile level of use; covers wide range of loseless formats; has EQ; Last.FM compatable; fills gaps in metadata; full scale or minimal appearance; more features than other freeware; application for iPhone; offers device hog mode; warmer than iTunes; clean/streamlined/easy user interface; commercial audiophile offerings are noticeably better.
The top contenders are all commercial: Amarra, Audirvana, Bitperfect (last place in this list but only $10), Fidelia, JRiver, and Pure Music. Which is best depends on equipment synergy (they all sound good), individual needs/taste (mostly of the user interface/features), and which version of which you've got (this is a fast moving field, any advice will be out of date before year's end). But all have trial versions (some not completely equipped) and even fully versioned, the price is comparable to what you'll probably spend on a USB cable.