OP here again. Wanted to provide an update. Bellwether Coldfront fell through, but I found a Gore Performance Shell at a clearance price of $50 which I couldn't pass up. So, I'm now waiting for temps to drop to mid-30s at which time I'll try my UnderArmour coldgear jersey with the Gore Shell. I have a feeling I'll require even one more layer since the Gore Shell has very little insulation, but I'll need to wait for lower temps before I know for sure. Will provide results soon -- hopefully not too soon since I'm perfectly fine with 60 degrees in October.