I chose the lowest choice. 20k-22k
It might be worth noting, that the price difference between Direct Injection, and non-Direct Injection versions of the CTS is a mere $2300. BUT that upgrade also includes the 6-speed automatic, which is itself a $1250 option in the Corvette. Not to mention the whole idea of having an "uplevel" vehicle (especially a Caddy) means you have to pay a little extra for it...
So in reality, all else being the same, the cost difference between the two engines should be just under 1000 bucks. If a non-DI V6 could ring the Camaro in at $21,000. Then the DI V6 should be able to do it at $22,000 easy.