Sorry, I forgot to mention I'll be going with either the stock 265/40 PS2 18" or 275/xx (can`t recall which sidewall I have) 18 PS2, not the Cup tire spec listed below.
And thanks for the reminder!
(I'm going to hit the online calculators tonight and determine which is optimal)
Grey Matter:2008 E92 M3:608/425. SG/PS
Dark Matter:2015 F80 M3:495/505. AB/CB