Take rear w/3.42's out of formula for free???
It is MUCH more involved doing a gear swap than it is a whole rear-end swap. Plus if you ever want to "upgrade" (if you want to call it that) to a 3.73, you'll need the 3-series carrier from the 3.23 or 3.42 ratio diff. The 2.73 uses a 2-series carrier.
IMHO, the 3.42 is the perfect choice for an A4. I just installed a set of 3.42s to replace my 2.73s. I like it.

