Well, if your installer still has stock of 1k.2's, that's what you'll get. There's not much difference, IMO, between SS on the 1k.4 and the 1k.2. I think the only reason Dish is going to the .4 setup for EA & WA is to simplify things a bit.
With 1k.5, my SS is up maybe 5 or 6 points, which really only helps with rain fade, nothing else. BTW, the only reason that I have a 1k.5, is because I had a 500+ laying in the garage, and decided to experiment with it.