A 20" wheel is for ricer cars on something this size, if you buy an ST and want performance that is the last thing you would do. Sorry if I offend anybody but I have been modding cars for 45 years, 10 of those 510 Datsuns, I built the first turbo 1ZZ Matrix, 17x8 RPF1 wheels, second fastest SM can in SoCal, raced Vettes, just sold a 500HP 2300 lb 95 M3 I was building, and looking hard at the ST as one of only two cars that will fit in my trailer we are going to travel all over NA and drive on all the great tracks with.
I have a 318ti project car, 300HP, same weight, size(larger interior), weight, I am currently building but once I get to drive the ST I might just change to it but I will have to REALLY like it and of course mod it, not enough power, audio, sound deadening, wider light wheight wheels which seem none existent for now.....
I have a new Duramax dually and replaced the springs with 3/4 ton, removed the overloads(80 lbs of unsprung weight) and added air bags to take care of the hitch load of a 19000 lb trailer and it rides far better than stock, far better than our V8 4runner with high end shocks and air bags even, actually handles incredibly well for an 8k lb truck!
No offense meant but the reality is real performance and what some think is performance is not in the same realm. I do respect your right to do as you wish, I do not understand why as a lifelong modifyer but to each his own, do what makes you happy
Rick