Sending DMs to users in a forum: what would be your approach?

[99lives]

I have started a new forum on a niche. 3 other forums are our competition. But we are a greater one, with better material and more experienced users.

I would like to direct message members of the other 3 forums. So, I'm not sure how to approach that task. Should I hire a xrumer provider to do that? Or that's not a good idea?

What do you think, guys?

PS: the forums are SMF, vBulletin and PHPbb