Hmm... Six to eight feet, docile and cool looking. There are quite a few options for you. All snakes are cool looking (to me) and personality is relative, but the animals below are in your size range and generally even tempered.
Male red tail boas grow to about that range and for good karma you could get one from a reptile rescue. (be sure it's male since females would grow larger.)
Black rat snakes can grow that big, and come in a variety of morphs.
Pine and bull snakes are large, impressive, and I've only read about them, but they're apparently pretty nice animals.
I'm sure there are many I'm forgetting, but those are the ones that come to mind.
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