I've got at least 30-40 of them in one of my 20g tanks. If you don't get them in with your live rock I'd wonder how "live" you rock really was. Bristle worms are harmless to 99% of animals. Some people have said that you should try to decrease there numbers if you plan on getting sea horses, which you couldn't do in that tank at this point anyway.
If you decide for some odd reason you don't want them most LFS, including one I know in Newark, sell little things you can put in the tank to remove them. If you bring them to the RC meeting I am sure someone would like them.