First off, $30/hr != 60-65k/yr. Despite the silly math they use to convince you. The agencies around here (I'm in the same area) don't have any worthwhile benefits that would actually justify driving down the rate that much.
If you've already been submitted, they've quoted a rate to the client. Unless you absolutely wow them in the interview, the client isn't going to want to negotiate. If it's IBM, like I'm guessing, they're pretty much fixed on the rate for the job, no wiggle room.
That said, the agency I *know* has built in anywhere from "some" to a "boatload" of wiggle room. I've never met an agency that wouldn't budge some if you interviewd and have an offer on the table. Less money for them is better than no money. Of course, at this point you have to have the negotiation skills to get them to wiggle... see the other posts already here.
Oh and the rate isn't bad, though you can probably get more. If you don't have any other options it's definitely worth taking over unemployment.