in the a3 fwd i'd think it'd be ok, but in an a4 thats asking a lot from a 1.6, i'm sure it'd be put under a lot of stress with passengers
why not go for a tdi? or 1.8 if going for a4
tdi will be much cheaper if you do a lot of miles in and out of town, if you only have it for the 5 min shopping run once a week, thats different