Don't dick around, get a C90 or B200; or as Chuck said, a nice C425 or 441.
IFR CHTR approval is not that difficult for a PC12 either and that would suit your stated purposes admirably.
If the budgets not up to a turbine, go a C414 or C421, or a C404 if you don't want the pressurisation. A good PA31 310 or 350 is also worth a look (I have a very sweet low-time refurbed one available). Forget the Panther mods.
If your budget will struggle with any of these options, you're kidding yourself; stick to the 206.
No '6 seat' light twin (B55/58, C310; AC50; PN68; PA60 etc) will be any good for filling the seats. An Aztruck would do it - mine did an honest 170kt with 6 x adults - but like all light twins, they are all getting old.