If you are on budget, pick Cirrus SR 20 or 22. It has speed. consume around 11 gallon per hour. Lean assist. Roomy inside. Great for passengers on board. And FAST.
Hostile terrain? No worry. CAPS is there. Fly airways.
Pilatus PC 12 if you have loads of dosh. Much more comfortable. Pressurized. More loads, more heads, higher cruising altitude. FASTER.
I assume that your 6000 nm journey does has a few stops for refuelling.