From previous experience with a C7 Z51, I would forgo the Z51 on the C8. I do like the eLSD and the lower gear ration, but not $7000 worth. I modded my C7 so it has about 540 hp at the crank and reduced weight by a 100 lbs. Some bolt on mods will get the base C8 to that 2.9 second 0-60. The shocks and rotors can be changed as can the tires. The Z51 adds about 50 lbs. to the car, which isn't much, unless your on the track.
I'm curious to see the aftermarket performance parts for this car. I would wait at least a year for some R & D to see what the manufacturers can come up with. The C8 looks to be an awesome car, Hats off to those that will be getting one.