Yeah that's a good point about a brown PA(and FA?) working in pretty much every situation that would call for a black PA. I also already have a half brogue in a dark color (the burgundy Sanfords).
When you say the Magnannis aren't as "nice" as the PAs - are we talking mostly about bologna construction vs goodyear welting or the quality of the leather? I think I actually like the shape of the Magnannis more for a plain cap toe than the PAs, though I'm not sure they'll ever be as comfortable. I'm also not sure they're really worth $130.
No brown Parks, but I have the option of a Brooks FA in Brown. Basically, if I'm going Brown + Walnut, I can decide which is a Strand and which is a Fifth Ave. I pretty much have to choose between two of the following:
(all BB seconds)
When I say "nice" I was talking about leather soles, goodyear construction, and other details. I can't speak to the quality of the leather, but I'm assuming it's higher end. I suppose "nice" wasn't the right word. "Higher-end" is probably a better way to think about it. I briefly checked them out on the Nordstrom website, so if I'm incorrect on any of that, apologies.
From that list, I'd go brown FA and Walnut Strand if I was choosing for myself. People will disagree, but I don't think there are many practical difference btw brown FA vs PA in terms of situations where you would wear one vs. the other.