radium MP3 codec (based on Fraunhofer IIS MPEG Layer-3 Codec) is by far superior to anything else ... and it can be used with any wave editor - soundforge, wavelab, cool edit, etc
As for the difference in quality between encoders. Xing's encoding algorithm just plain sucks. It's slow, cuts off some highs and some lows, and I've found that there are intermittent periods of hissing in the background when encoded at any bitrate.
I'd suggest CDex. You can get it off shareware.com. It's the fastest I've found to this point, and it still maintains good quality. Also not a huge download. Comes with the Lame codec.