They are different types of cars so you need to figure out what you want out of your next car. For pure speed, the WRX with mods is it. For a tail-happy 2-seater, the NSX. The S4 has it all: looks, performance refinement luxury. You need to decide what kind of car you want and the mods you would do to it. Sure you can sink $5k into power mods for thr WRX and make it hella fast, but if you aren't actually going to do that, then you're always left driving a $13k ugly sedan every day with serious turbo lag.
I'm not a fan of AWD. I'd look for a CPO M3.
Aaron
