it all depends on what you want... you said you want to get into some autox.... but how fast do you drive say on the freeway, do you race anyone? you want to make sure you dont get geared to high. In that case you would fly to your top speed, but as you probably know the top speed wouldnt be that high.... personally i really like the 3.46
if you want a comparision of rpms to mph with different diffs go to
http://www.diffsonline.com/
and click rpm/mph and pick with diff you are looking at
Hope this helps you out
David