the cost of the Z06 and the performance you get are hands down hard to beat. with just a more agressive alignment the car handles way better than stock. add the T1 sway bars and its even better. the only other thing i have done handleing wise is C6 Z06 shocks just because the 01' shocks sucked. parts wise brakes are cheep and so are parts unless you do something odd ball. rotors depending on how hard you are on them 6-8 track days is all you'll get from them. but at $50 a rotor who cares.
now at the on a road track i run my street tires. autocross i have slicks and they are worth 2 1/2 to 3 seconds on a short half mile track.
as for the EVO and STI, on a road track you will not even stay close to anything else you have on your list. and depending on the driver nor an autocross track, if you have a good driver then yes you will run with and sometimes in front of them. but put those same drivers in a RWD car and i would bet money in most cases they will run no where near the same times. if you want to be a good driver then learn RWD and FWD before you do AWD. IMHO an AWD car is like a bandaid for a bad driver, it will cover so many mistakes. just like you learn to drive on street tires before you go to slicks, slicks cover up so many bad habits that street tires would show.
P.S. Ben, off track in a vette really isn't that bad, i did it in the rain at Nelson. it was in a really flat spot though and i didn't really even slow down to get back on track.