my 235/45 does not have noticeable stretch. It doesnt quite use the rim protector on the ideal angle, but it is FINE... I can give you photos tomorrow of how MINIMAL the stretch is.
Supposedly 180rwkw... really should put my EBC in and wind it up ey . So I guess Can't really compare given you have ~100rwkw more.
I dare say my car is a little lighter and stiffer than yours though(with a 2way), and I wouldn't say I struggle for traction. With shitty neovas, I did. If you are going for max traction on a budget, maybe go 245/45 for the extra sidewall? and its cheaper. A light stretch on the front will also feel better, and be cheaper. I assume you are keeping an eye on the wallet given your options. PM Ash and ask him what Tyres he was running, he had similar power to you with no issues, now has more I think.
The 45 series is cheaper and has a higher load rating, something to keep in mind.
235/45/17 KU36 $164.00 94W
245/40/17 KU36 $215.00 91W
245/45/17 KU36 $202.00 95W