Wider tires on 17" wheels outperform 19's

Need some advice, I have to stay with a 17" wheels or move up to a 19" wheel due to Stop tech big brake kit on my roadster. I know 19's have a better appearance factor going for them but I am wondering if going to a 245/45/17 F and 245/50/17 R will work just as well if not better than 245/35/19 F 275/35/19 R from a performance stand point ? Perfomance is my number one priority then looks.
I am also concerned having read a number of threads about having to add lowering springs to keep from looking like a SUV roadster. I managed to confuse myself enough on this and I am looking for input.
BTW: I have decided to go with with SSR professors (black with polished rim on SS 350ZR) make any difference?