Inexpensive and power efficient refurb PCs for firewalls

This is a follow-up on my earlier post about the Lenovo M58p (Intel Core2 Duo E8400 @ 3GHz) that I'm using for my home firewall.  It clocks in at 38-40W idle and 50-60W under load (which is rare).

If you go to NewEgg's site and go into the Desktop Computers category, you can find all sorts of refurbished boxes for under $150.

So what sort of CPUs are there and how do they stack up in terms of TDP and idle TDP?

Well, according to various charts on the net:

Intel Core 2 Duo E6600 and E6750 should both draw less power then the E8400 that I'm using.  At a guess, that would put total power draw closer to 30W idle rather then 40W.  The Core2Duo line also performs better then the old PentiumD and Pentium4 chips when under load.

So Core2Duo is better then a Pentium D or Pentium 4 chip, and the slower E6600/E6750 C2D are better then the 3GHz E8400.

The i3/i5 series (Sandy Bridge or later) should offer lower power-draw then the older Core2Duo chips.  Power draw dropped again slightly with Ivy Bridge and Haswell.

That being said, the least expensive i3 refurb is $220-$250, while a Core2Duo unit can be found for $80 or less.  So I think until the i3 units start being retired in another 2 years, the C2D units are going to be the best choice.