This is a no brainer. Viper first.
Here's why:
I'd want to be able to enjoy the performance of the Viper when I was young. When I'm an old fuck I probably won't be able to drive worth shit so why would I need a Viper when I'm old. Plus, if I had a Viper when I was 16 I wouldn't live to be 46. So I'd never have to drive a Yugo anyway.