If you are considering the Thunder Mustang, then you are considering non-certificated as well as certificated.
If this is so, then you may want to look at the Lancair IVP and the Turbine Legend.
http://https://www.facebook.com/turbinelegend
Both these aircraft can be obtained within your budget and certainly meet the performance requirements that you have stipulated wrt speed and range. I'm not sure of their runway requirements though. 800m might just be within their capabilities but I am not certain.
The IVP would certainly give your man some space as it is a 4 seater, whereas the Turbine Legend is a 2 seat tandem but with a fairly big cockpit.