I would say your quant background is slightly above average for accounting PhD applicants, but it will be evaluated along with the rest of your profile. In general, accounting PhD applicants come from two pools.
The first pool consists of folks with an undergrad and typically also a masters in accounting that have professional work experience and typically a professional designation (CPA/CMA), given the degree requirements of these degrees and the fact that most 20-21 year olds have no idea what an accounting PhD is, these individuals usually do not have a very strong formal quant background. The second are folks without an accounting background, but a strong math and economics background. Then there is a small pool of applicants with both a strong accounting background and a strong quant background, but this is a fairly small subset of the total applicant pool. So overall, your quant background will be viewed very favorably if you also have an accounting background (which is does not sound like you do). If you do not have an accounting background, then I'd say your quant background is about average for the subset of applicants coming from the quant/econ pool.
A question you will certainly face, if you do not in fact have an accounting background, is why accounting? You will want to make sure this is something you can clearly articulate.