I came across an article on A Practical Wedding entitled, "How to DJ your own wedding." Sounds crazy, right? BUT, it would be SUPER cheap (assuming renting an amp system would be cheap, or FREE!), and it's a guarantee that the music played would be what we wanted.
How would that work, though? Orchestrating music during the reception introduction would be tricky, but dance time would be a cinch!
One reader had a pretty good idea of ensuring the playlist is guest-friendly: