I have a contact at one of the big four, working in human resources, and from what I was able to ascertain from her was that firms like the big 4,GT,McGladrey, and pretty much anything in the top 25 vault rankings will have a very structured hiring process mostly stemming from on campus recruiting. Within this processes, where these firms hire pretty much all of there intern/entry level hires, she said the absolute minimum gpa is a 3.0. Unfortunately, anything below that is not even considered unless there is something else that stands out.
Some exceptions that would apply would be if you have super strong work experience, or a good contact at one of these firms who is willing to go to bat for you. As far as having your CPA all passed, that is definitely a plus, but I was told that this is not really as important with the top 25 firms as they like to develop internal hires. Basically, and I hate to say this, a 2.6 is going haunt you for quite a while, most likely until you have either gotten a masters or have been working for about 3-5 years (when you may not need a gpa on your resume).
My advise would be to think long-term; network like mad to get into the best firm you can, even if it is a 3-person local cpa firm. Once you have the CPA certification and a few years of quality experience under your belt that you can speak confidently about, you can tweak your resume in such a way that your gpa would be a non-issue. In fact, my contact at big 4 specifically told me that she has hired a couple of people with this same background, and while it doesn't happen very often, it is definitely something to look forward to.
What exactly are you goals for the future (firm size, public/private, audit/tax/etc?) This will help assess your specific situation.