I really don't think that "upgrading" the front brakes will achieve anything. As others have said, a good working standard system will lock the fronts wheels fairly easily. I would suggest you check that the pistons in the calipers are all working, change the brake fluid and check the rear wheel cylinder is not seized or leaking. I don't use the brakes much in normal driving, just taking your foot off the accelerator slows you down quite a lot with engine braking. There isn't a big choice in brake pads to fit the M3W and harder pads will not help, standard ones are fine if the system is working correctly.
