Since you're still a few years away from applying to business school, would you consider taking classes at a more well-established univ to get your overall GPA higher? That might be the best bet. Your work experience doesn't feel unique enough to set you apart. Many CPAs will likely be applying at the same time as you, and many might have a more traditional educational background. A good test score will help, but I think getting the GPA up will likely be the best single thing you can do to help your chances at a top program.
hope that helps,
Former Kellogg adcom member, offering a new approach to MBA Admissions Consulting.