S6 specifications vs. 90Q 20V

[Brian Pleet <pleet@sfu.ca>]

I'm the orginal owner of a 1990 90Q 20V with 102k km and am looking at a
potential upgrade to a newer Q. The dealer has just brought in a "demo"
96 S6 and I took a long look at it today. The wheels are 15 inches and
the tires are Goodyear "Achieva". Something doesn't look right. 
 
Were these the original wheel/tire combo on the S6?

Are there going to be major differences in upgrading to this car? I've
signed up for my first Quattro driving school in Limerock CT. Is this a
good time to switch.

Brian Pleet
Halifax, NS, Canada