Those of us who love our Mustangs pour all our money into them and then we start going further. I think we hit the point of "bolt-ons and then some" and start looking for more.
I don't think any of us realize these cars are also our daily drivers until we're caught in the middle of a monsoon with our slicks - which we then have a solution to. No tire for our car is ever "how is the wet traction?" but the question is "how scary is it at speed" or "how does it hook at the track? Okay, good. Those are my new tires." The hell with street tires!