great info, thank you for helping me think through this.
i'm going to get the 13-23 cassette to start with. i think having the 18t cog will make the difference i'm looking for. that will allow me to stay in the 53-16, 17, 18 most of the time, right in the center of the cassette. i doubt i would need to go down to 50T if i have the 18t.