Post Bac, I'm sure, is a non degree. You basically get all the perks of a graduate student, you just get absolutely no degree for it. Studios are usually available, crits with professors and your peers. Just no degree.
And yes, the graduate level hours look great for your next round of applications. And you could probably get some pretty good rec letters out of it too. Like I said, if you can afford it, GO FOR IT! If you are looking to improve your work, that's the way to do it. Another option instead of post bacc is applying for a residency. Once you apply, some will actually pay for you to go. And there are different residencies for different amounts of time-between a week to a year. Looks just as good as post bacc on a resume or application.