it seems as if it will be almost 2x cost effective to just buy the dawes SST. It will cost you well over $500 in the end for reasons already mentioned. You can buy the SST and use the $170 price difference to buy yourself those DP18s you want. Then sell the Alex R500s and have some money left over to buy other parts as you see fit.

The logic that you'll be spending money here and there while building a bike as opposed to spending a chunk of cash at once for a complete bike doesn't make much sense to me, considering you'll have to spend a chunk of change before you can even ride your bike build.