I am using GarageBand, the Podcast format. The Podcast is good because if you record your "3-2-1 Start" and "2-1-Rest" as the Male or Female voice, then the music will automatically fade in and out. It is a little clumsy in my implementation above, but that's just working out the details. If you drop a 5:00 minute or 4:00 track it will auto-fade in and out for a pretty smooth experience.
GarageBand is a Mac program - I don't have much idea what you would use on Windows. I think you could use QuickTime Pro ($30 license I think), but I am sure there are alternatives as well.
If you want a track of just counting, with no music, let me know.
No other comments? Come on folks, tell me what you are looking for. Give me some good ideas, and I'll implement and post for everyone.