Common misconception that adding power increases your cruise speed, it becomes very inefficient very quickly. And if the engines are all that changed, Vne would still be the same. All it would mean is you could climb faster, and possibly carry more weight.
Other advantage of the C208, assuming same speed/load capacity - 2 engines. Not a huge deal for most pilots, but for those punters who reckon a baron must be safer than a PC12. Oh, and Capt Wally.
From what I know about gipps, they aren't exactly fools. They wouldn't even consider this if there wasn't a definite market out there for it, even if it's mostly export.
And to those who reckon Oz is too small to have someone building a twin turboprop, try telling Embraer not to build jets cause they mustn't have the infrastructure, or the market to sell them!