I don't mean to brag here, but I find both AUD and BEC to be easy; FAR - difficult and REG - insanely difficult (due to lots of factors).
Seeing that you've already passed both FAR and REG, I want to encourage you: AUD and BEC are very doable. If you'd be able to get BECKER for AUD, then you'll definitely pass AUD on the very first try. (I've studied AUD for 4.5-5 weeks: textbook, homework MCQs). In my case, some 40-45% of the MCQs on tha-a-at day were exactly from the Becker's testbank of MCQs. Word by word! Beware that AUD is the trickiest of all four exams. Becker teaches you how to spot those traps.
BEC is a slightly different animal: some say it too easy, some say it's confusing (especially the cost accounting and finance stuff). I took some classes in both areas, thus I've spent only 2.5 weeks to prepare for BEC. But Becker makes everything even clearer; it gives you a "structure"! I don't particularly like everything about Becker (I had some software expiration problems with them), but Becker found the right key to unlock the code of the cpa exams.
I have to tell you that I'm a very slow test-taker, but I was able to finish the BEC exam with 40 min. to spare. The BEC part was not adaptive (which helped a lot!); I don't know about 2011 changes though.
So, find some Becker review textbooks and MCQs (even older versions) - and will forget about these exams very fast.
All DONE!!!
Freedom is a beautiful word :-)