Why are you looking for improvements in tdp?
I have an Ivy Bridge 3220 that have never, ever exceeded 20w with one core at full load unfortunately no software i am using on it runs more than one core, and I presume that given two cores the total power consumption will not exceed 40w. And since full load is but momentary, not more than 10% of total processor uptime, i doubt your average consumption going from Ivy to ULV will drop by more than about five watts.
That difference, when given one thousand hours, will have saved about five units. At the highest urban rate that is about fifty rupees, give or take.
I don't see the noise about power consumption relevant with desktop parts. In the end the savings are simply not substantial and are easily masked by differences in say, PSU efficiency. When it comes to NUC, it's still quite expensive for what you get. About 20k plus a disk and memory, you could easily build something much cheaper. Atom unfortunately regressed in its second generation, and hopefully it will die soon.
If you are looking at the lowest possible power use for desktop tasks, get an ultrabook if you can live with the form factor, or a tablet. Battery use means zero consumption, and charging is more efficient than sucking down power with a screen and a bunch of fans and disks.