I've built community and support from scratch at seesmic, uservoice, and launchrock. And, we worked through this same question at my current company, primeloop.com.

Desk, Zendesk, Uservoice, etc. are all great support platforms (and there are hundreds more). But I would skip all of those when starting off, and go straight to http://intercom.io since you can handle support through there, but you also get a full CRM and drip-messaging right out of the gate.

I'm more than happy to talk through your setup if you'd like to hop on a call?