The original wire stock from sig is my favorite but they're going for a premium now. The minimalist plus works well. The minimalist is a little too small for my personal taste. Not a fan of the folding/ collapsing sig offering. Kind of defeats the purpose some but the folding 1913 knuckle will let you go with any carbine AR stock.
ETA: The ACR stock with, a pic rail adapter, on the pic rail mount is more pieces than you need. The LIFE ACR adapter will let you use the ACR attached directly to the "stock" mount on the xcr, removing an extra piece and reducing an already long LOP.