The car's brakes will overtake the tires in stock form. I'd start with SS lines, better fluid, and better rubber before plunking down lots of cash for bigger/better caliper/rotor combos.
Does your car have a LSD?
The triple Webers and a Euro motor are a good combo. I guess the real question is, do you have a goal in mind in terms of power? A fully built NA M30 (bored, stroked, 10:1, cammed, FI, the works) will hit ~250rwhp, but cost ~15-20k. (assuming some one else builds it for you)
A S38 or M88 (the DOHC versions of the M30, used in the E34/E28 M5, E24 M6, M1, and SA 745) will make about that much stock, and can go much higher NA, but is also much, much more expensive to both build and maintain, much less find in good condition. It will also require a firewall modification to fit due to the wider head. A few on the board here have done that swap, and can tell you more.
Like I said, the main question is, what are your goals?