Lacing for the rear should be whatever gives you the most tangent spoke to the hub flange. For 32h that will usually be 3x.

Just an FYI, but I believe the IRD Cadence Aero is the same rim as the Kinlin XR-300. If you are ordering from the BHS anyway, they carry the Kinlin. If you haven't seen it already, you may find this rim comparison useful: http://fairwheelbikes.com/c/forums/t...3-rim-roundup/ It seems you may do better with a pair of either 270 or 279s. At any rate note that the A23 really doesn't save much weight over the Kinlins. I believe they originally were spec'd at 426 grams, but in the real world they are heavier.

I like your choices in hubs. I have used that BHS Wide front on a couple of wheels and it has performed well. And the Ultegra and WI are both strong. Note that the H3 has been replaced with the T11 which is 11 speed compatible.