My sith will follow the code of the jedi. He is not a sith because he lusts for power or material objects but for knowledge. He believes that the force should be fully used and not limited by the laws of "man" (I use this in a broad term, not humans :P). He does not believe that the killing of innocents will bring him anything and while he follows the ways of the jedi, he does not believe that they do what is best for all.
I actually think it'll be more fun to play a good sith. Being evil is easy as you can just keep killing people and wracking up the dark side points like M&Ms. If you've ever played KotOR you'll know how hard it can be at times to pick the "good" answer. Remember the peasent in KotOR 2 when you first enter nar Shadda?