When auditioning a whole bunch of people or getting MP3s from people... what's a nice way to say thanks but no thanks without hurting a guys feelings or even worse, making him want to stalk you with an uzi some time in the future?

Like, I meet these great people online who give this great buildup about how good they are. After several emails, I finally get an MP3 from them and realize that they're about 20 years behind me in terms of playing experience.
Or they have absolutely nothing to offer in terms of anything that I couldn't do myself. Or, no recording experience.

How do you turn somebody down after building up a friendly email reletionship in such a way as to make it clear that you don't want to work with them but not completely close the door to future working relationships? (just in case the guy makes a million bucks some day)
(I'm looking for serious answers btw, not smart ass replies)