Core Player is the commercial version of TCPMP and is better in some respects but worse in other, or so I hear, I've never tried it myself.
You can find TCPMP in the download section of this site and Unit Zero has put together a package of all known codecs for it.
Look here.
You may be better off using WMP if you really like WMA, I'm not sure if the codec for wma will work with the X5, it does for WM5 and 6.
Have a look, give it a try and see if you like it, most people do because it works with a huge variety of file types.