I did a job last night and there was no distortion at all on none of the mp3's. The only thing I did different was I didn't use my laptop output booster. I have this little output booster that I bought at Radio Shack that you plug into the output of the laptop, which happens to be the headphone output, that gives a little boost to the output of the computer.
On my next gig I'll try using it again and if I get distortion I'll know that that's the problem.
I'll keep you posted.

Thanks.