Go with option 4, keep the M3 and Denali and buy an X5M. I see you track your M3, so an M5 wouldn't be a good track car. It's just way too heavy. Let your wife drive the X5M as a daily and ship the Denali up North as beater. The X5M has 6,000 towing capacity and you can put it to better use here in CA.
Current: E92 M3 DCT, Cayenne Turbo S, Ferrari F430 F1
Past:911 Turbo (996), C32 AMG, S2000, (E36) M3, Supra TT, MR2 Turbo