i have a 300zx with 330RWHP and 350RWTQ.. i want to buy a 540 or an m5. how would the 540 stack up against my z? how would the 540 stack up against an m3? it would be an 02 or an 03. i'm keeping the z. i just want to know. peter ps.. any known problems to look out for? i'll probably be buying from a BMW dealership.