The Nepal Extremes should have kept your feet plenty warm. A couple years ago I had experienced the same symptoms with my Nepals. Turns out I had them laced too tight, they didn't feel like they were but after making some adjustments everything was good. Before you give up on these boots fiddle around with the lacing, you may find that a different boot is not needed.
At this point in my life I should be daryl5.3 not daryl512