"This may be simply a Garage Band issue. Or perhaps a Mac issue. I don't know sh*t from shinola about recording and don't do a lot of recording. I convert Garage Band files to WAV if I am going to send them to some one. I always listen to the WAV file before I send it. Sounds like the Garage Band recording. I occasionally get comments from the folks I send the recording to, however, about too much reverb. At first I thought it was a matter of personal taste, but as an experiment, I e-mailed myself a copy of the WAV file and compared the e-mailed recording to the WAV file on my computer. They are undeniably different, and the reverb on the e-mailed file is definitely excessive"

This doesn't make any sense. Nothing happens to a file when you mail it to somebody that could possibly effect the amount of reverb featured. It's the same file! Any more than if I were to copy and paste the words I'm typing now into an email and mail them to me ... they'd be the same words. Now if you were talking about converting a WAV to an MP3, it might start to make sense... Could you post a "Before Emailing" and "After Emailing" sample on soundcloud or something?

As for the Mudcat CD, that's no mystery. It sounds like whoever mastered it was a bit heavy-handed and uniform in getting the volume of the album up to a "professional" level.
To do so, generally Compression is used: this makes the loudest parts of a song (or album) quieter, but leaves the quieter parts untouched. It allows you to then make the whole thing louder.

That's all well and good for music that's fairly consistent in its volume level, but it does no favours to very dynamic music.