Conduit punch, or a different drill? I think I would use a different drill more!
Well, yes, a nice DeWalt Lithium 3AH hammer drill cordless would be a nice xmas present to yourself. The issue here though, if I'm assuming correctly, is that you've burnt up a few bits on the same hole already. The only way to get further if you haven't gotten to your desired hole size is to avoid that work hardened edge entirely. A conduit punch would do that for this particular hole. If that hole is already done.... disregard. Hmm, well a conduit punch/die set is still a pretty awesome thing to have in the toolbox.