Hi
!
I should recommand to every 1Addict to swap the rear tires with 255's ones
! Your car will be more stable, you will definitively have more grip (what are the specs of your actual tires ?).
For example, I swap my 120d (Ok, not really a sportcar but a dieselsport xD : almost 225hp / 345lbft) to winter mode with 225 rear (and 205 front) Pirelli and I missed I had less sized rubbers when I turned the first day I drove with them ... I drifted a bit ...
When I previously had 205/225 (r17) for summer tires, I hadn't this terrible grip and precision I have now with my 225/255 (r18) summer tires
So yes, definitively yes, go to 255.
Moreover, I would recommand you Mochelin PS3 or PS2 which are said to be a very strong combo for our cars