S4, 330Ci or old M3

I want to buy a car and I have it down to an '00-'02 audi s4, an '01-'03 bmw 330Ci (coupe) or like a '95 M3. Im in love with beamers but audis are great too. Im going to really mod this car im just wondering which looks better, what is a better buy for the money and which has more potential for performance. FYI i know a good amount about cars and these ones just need some advice. Thanks