Thanks for the detailed thoughts!
Yes I know that Bourbon and Walnut are similar. I really love the Walnut shoes though.
When you say Brown in #2 are you saying Brown Burnished (ie dark brown)? I haven't really considered the dark brown as I was thinking of the Bourbon Stands serving that role.
Regardless of brand, I'm referring to a brown captoe, either a "punchcap" like the Fifth Avenue or a plain captoe like your PA. And, yes, in a darkish brown. Given all the suits you wear, assuming you wear mostly suits all week, I think you need a second dark, traditional captoe to go with your PA. I don't think AE's bourbon - though gorgeous - is as versatile as a darker brown, nor do I think a medallioned, "brougued up" shoe like the Strand is as versatile for suits as a punch cap. I know others disagree. Combining those two characteristics for your #2 suit shoe is not something I would recommend.
While something like the Strand in walnut is very good for certain casual and seasonal suits like those in linen, seersucker, and poplin, I just don't think that color would serve you well as a year round, workhorse "suit shoe" in a limited oxford-bal rotation.
Note: I freely admit many folks here wear their walnut or bourbon Strands way more liberally than I would. I'm probably throwing out a minority view, or at least a conservative one. Just my two cents. I'm sure you will enjoy whatever you pick.