Hmm...if this is going to be a commuter, why not just get a nice touring frame (or use your current since the measurements seem right), and consider throwing a carbon fork on it if you don't plan on using front panniers. That would cut down weight by a decent margin.

Only reason I even mention weight, is my DB mountain bike turned commuter with rack and all weighed about 35-40lbs, and even I found that bike to be a tad unwieldy whenever I had to carry it anywhere.