B4 or not PA is a stepping stone in your career and for a majority of people, the lifers (as they say) have literally no external private experience (much like professors teaching Accounting straight from their phd's).  You can learn a great deal and have a solid background coming from a regional or local firm.  I was successful for a regional top 10 firm and I know I would have been with the B4 or a small firm but I was just comfortable with the firm that I chose as in the people and culture.  I have met some poor 4.0 auditors from the B4 in my lifetime and some great 3.0 auditors from the regionals, the B4 stress GPA as an entrance given the large applicant pool.  Point is you can have a very successful career without going to the B4.  Trust me I know ;)