The sc430 replaced my Z4MC and it feels like a boat compared to the MC. But I do respect the sc for what it is, effortless luxury.
Really doubt there would be a big difference from the mk1 or mk2 SC tbh, compared to what I was used to.
I have the 6 speed on my 2011 is250, and having the 5 speed sc really isn't a hardship.
A low mileage car is going to generally feel "newish" compared to a high miler.
Would easily be worth 3/4k more than a high miler, especially when you take into account the cost of the car when new.