AFG King Air 300 is as close to a payware King Air as you can get, but for free, with many working switches, VC, and cabin; though you need to find the FSX patch, if your using FSX. The model simply blows the default king air out of the water... which may or may not change your mind on the prettiness of the King Air (personally, I like how King Airs look

).
Around the same type of airplane, I'd probably go with something along the lines of a Piaggio Avanti, which is a high-speed turbo prop that pitches around the same range, but is a bit faster than the King Air. Very sleek looking design too and flies extremely high for a turboprop. I only know of Wilcopub's payware model, which I haven't tried, but you can have a look at it at
www.wilcopub.com. The Cessna Mustang business jet may also be your cup of tea. A bit faster, and your getting to the realm of turbofan engines. Very sleek looking business jet, but has less range than the King Air, ironically. Flight1 has a beautiful model for the Mustang.
Aerosoft has a payware Cheyenne that is pretty good, and is a comparable aircraft to a King Air. Its a touch slower, and in my opinion, this Piper turboprop isn't as sexy looking. Looks are a matter of subjectivity though.
Premier Aircraft Design has a freeware Mitsubish MU-2, a plane considered in the same class as the King Air. A little bit faster, but like everything I mentioned aside from the Mustang and Avanti, doesn't quite run at 300 knots. I haven't really spent much time flying Premier Aircraft's models, so I don't have an opinion on them, but its worth checking out, since their stuff is free.
http://www.premaircraft.com/.