Hullo Andrew.
The original BIAB recording is the cleanest sound to my ears.
The trouble with mp3's is that they don't copy well and copies of copies lose more and more of the original sound and more mud gets added. Wav. files copy clean.

You have all the basics for a decent song so it's worth starting again from scratch if you have the stomach for it. I also lost files when I changed my computer and swapped from Sonar to Cubase and had to redo them.

Vic