There are very few, if any, SEP six seaters you can load up with 6 people and go any further than to the next field. And even fewer I can think of that can do it safely in all weathers.
Turbine, yes. Great if you can afford that. But if you can't, then a MEP twin is your only reasonable option. There's this huge illogical resistance to twins these days, but they are great choices compared to the alternatives. They will be cheaper to run and own than a SET, safer and can carry more than a SEP.
Let's use my Aerostar as example. Useful load 1640lbs. Load up with 2 adults and 4 kids, and you probably have close to 800lbs left. That's almost full tanks (141gal). That will get you 800nm with IFR reserves at 25gal/hr. Fully de-iced, pressurized, wx radar, can fly at FL250 and 210kts. All for the cost of $145K with newly overhauled engines.
Look at the alternative: buy a SET for $2 million. You can get a lot of fuel for $2 million - more than one can use in a flying lifetime - compared to the purchase of a SET. You won't go much faster and you still don't have an out when the one engine quits in IMC.
Bottom line: twins can do your mission for less than anything else.