I'd also say that the Meridian is a great option.
I voted for a twin, mostly because I don't trust TIO-540's. I don't like having two on my aircraft, and I sure as heck wouldn't want to trust my life to just one. A piston engine that big is a bit of a fire breathing dragon and if you don't treat it VERY well it will bite you. Now you've got to realize that the variant that I'm used to dealing with is one with 350HP, so it's got a HUGE turbo on it and I'm not sure if that makes the engine any more hard to deal with than a IO-540.
But with TIO-540's if you don't have the mixtures placed perfectly all the time the engines try to do. Any time you move the throttle you have to move the props and the mixtures. It makes a really busy engine on our installs.
I'd quite honestly rather have one PT6 over two TIO-540's. I know that stastically I'm safter in the Chieftain, but I'd rather be in a Caravan. High pressure fuel pumps don't crap out too often, and I'll take that over dealing with TIO-540's.