I have a somewhat similar problem -- I'm tempted to grab a merlot strand while they are available, but I probably wouldn't wear it as often as I would a mainline, always-available color like brown or chili. BUT if I'm going to get a brown strand, should I save up for one in shell? It's such a versatile design that it's difficult to settle on only one.
I have 3 pairs of Strands - Dark Chili, Walnut, and Oxblood. When the RDA sale comes around I'll almost certainly be adding Brown shell. The pics people are posting of it look incredible.