Why not try a lower profile?
Just fitted a Yokohama A Drive to mine. Its a 175/55/15 and the M3W feels much more lively and you can generally drive in a higher gear than you might be used to. Ok, you lose around 5mph at the top end, but how often do you go there?
I fitted mine primarily for improved acceleration and drivability in the higher gears for hillclimbing and racing, but I'm leaving it on for road use also, through the summer at least. It drops the back end by around 20mm
I did consider a 50 profile, but found there was very limited tyre choice and I also felt the back of the car would drop to the point where it might be too low for general road use. If you have adjustable shocks, which I don't, you could jack it up I guess
