If you want viable third parties, you want multimember legislative districts with some kind of proportional representation, even if it's just STV in small (3-5 member) multimember districts, and not something drastic like Party List Proportional or MMP.
Playing around with single winner election methods may be useful for some purposes, but it's not how you really get additional viable parties.
Playing around with single winner election methods may be useful for some purposes, but it's not how you really get additional viable parties.