Your not going to get much for that S600, with gas up their and its mileage its going to be a hard sell.
I'm a MB fan I don't see a Corvette as an upgrade. If I wanted a fast two seater I'd get an SL, or a CL. I hate cheap melted plastic action men interiors and rattles.
I know they are fast, but even the late model Callaway blown Corvette I went for a ride in was cheap. Fast yes, but it was like ok can't use the power your going to go to jail, cruising sucked because its like cheap and screams mid life crises. Fast car though, I was told it had 650hp.
Back in HS my friend had a 1991 that we beat the crap out of, the only thing that car was good at was burn outs!