Well, the Tecnam does 140kts but thats for a 4-place aircraft and a bulky airframe and flying low. If you design it for 2, keep it really slim, and able to fly high, i.e. pressurised (the key to high speeds), I can't see it being impossible. If the Aerostar can do it with 700hp and 6 seats (115hp per person), then a 200hp 2 seater should be able to get pretty close. The key to the Aerostar being so fast was that the frontal area of it was small - it was cramped.
The whole gas turbine thing is a dead end if you want low cost. As much as I'd like to, until someone starts selling a certified turboprop engine for about the same as a Rotax, it's just not feasible. And even so, with the fuel flow, it's a hard sell. King Air 200's? Yeah, nice, if you want to pay $10.000 for a one way ticket.
And IO, if money was no object, this is what I want. I can't believe you keep a spot for a Jetprop in your heart, when this beauty is around for the same cost! 1600nm range!
