I highly suggest
http://www.dewolfemusic.com/home/default.asp
I know it's expensive but music can really help on trailers and movies.
Plus if you break it down to say 6 songs a movies (1 per scene, 1 for trailer .. which you usually use more then that)... and say you do 4 movies a month (or 20 scenes and 4 trailers), thats about 288 songs a year. Which brings the cost down to about 17 bucks a song at the most. If your doing more then that ..it really brings it down.
xoxo,
Megan