I have an E90 M3 too you're going to miss the weight of the E90 but you'll love the TQ
Explore the E diff too, its more fun compared to E9x M3 diff and can handle the dimensions and mass of the M6 quite well. btw I have AMS catless downpipes and Kw V3 up for sale if your interested seems like you enjoy moding. PM me if you're interested. As it related to fitment w your wheels, I think you should be fine.