It's a bit late for me though, as I've already ordered the i5, but looking at it now, the cheaper ones do look a good option.
As you have not had a motherboard, you may not have opened the box of your i5. Many retailer will take back an UNOPENED Intel retail CPU. Alternately, you could sell the i5 on Ebay, where unopened retail CPUs often sell for more then they would at Newegg. Newegg does not take back CPUs unless they are broken.
Interesting looking in that article how the idle power in AMD vs Intel tells a different story to what previous SPCR tests have done [...] I guess the motherboard can make a big difference and it's so hard to make fair comparisons.
Yes, the difference in board powers can be significant. Overclocking boards can us a lot more power, due to the huge power supplies that they use. While normal boards never expect to deliver more then 95 watts (or 130 watts for extreme edition CPUs), overclocking boards must expect that they will be asked to deliver 160 watts to the CPU. Extra power circuits use a little power, even when turned off.
The H61 boards
are not for overclocking, and do not support extreme edition CPUS. They should use less power.
Chips like the Marvell controllers each use a watt or two. If your fancy Motherboard has 8 USB3 ports, that could make it draw another 4 watts at idle (1 watt per chip, 2 ports per chip). Add Firewire and an extra onboard NIC, and the overclocking full-featured board can draw another 15 watts all the time.
This board only has 2 extra chips, Marvell 6Gbps SATA using one watt, and a single Renesas/NEC USB3 chip using 1 watt.