Hi there, and welcome to our little corner of the Web.
I had a hard time choosing an exterior color too--mostly because I'd had a black car for seven years and was tired of it, but none of the other colors really grabbed me. I was attracted to Liquid Copper, but wasn't sure if I'd like it over the long haul.
To make a long story short, I went ahead with the Liquid Copper with a Graphite interior, and couldn't be happier. It's a real head-turner, and I get a lot of compliments on the color.
Anyway... Although Brick would have nicely complemented the Copper, I shied away from it as well as Willow. I can be hard on interiors--too many spilled coffees and burrito accidents in my past. I went with the Graphite interior for the sheer practicality of keeping it looking new longer. I don't know if you and your husband have factored wear and tear and cleaning into your decision, but it was the deciding factor for me.
As for your question, I personally think the Brick interior would look better with the Beryllium 16, as they are both warm colors. The Diamond Graphite seems too cool, in my opinion, to go well with the Brick.
The Beryllium was actually my second choice of colors. In the end, I chose something flashier, but whenever I see a B16 on the road, it still strikes me as a very pretty color--more so than the Diamond Graphite (no offense to any DG's out there!). I do think, though, that it's a color you'll want to keep clean and shiny, as it looks best when you can see the full depth of its hues. Bright sunshine really sets it off.
Hope that helps.
D