The 65W TDP A10-5700 on FM2 presents one of the most power efficient and balanced platforms for this scenario. Ironman517 is right as CPU performance is generally not important. GPU performance is, however, growing in importance as more and more functions in office and other apps are jumping on board the GPU acceleration bandwagon, for increased power efficiency. The A10-5700 has lower idle power consumption than the A10-5800k and Intel processors on LGA1155. I don't expect this to be far above idle that often. The A10-5700 is so superior for this situation that a comparison should not be necessary.
I fully support Ironman517's idea, although I would take on the A10-5700 or A8-5500 (65W TDP quad core APUs) for improved power efficiency. A mini-box seems innovative and just right. Just the only thing I can't be sure about is whether an AMD stock cooler would fit that, hm. However, there are other Mini ITX case choices.
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More than 4GB is completely unnecessary for the overwhelming majority of modern PC users - this can include gamers. I only bother suggesting 8GB when the extra $5-10 can't be used on anything else more useful in a suggestion or if there are apps like video editing or certain (but few) games like BF3 that might use more than 4GB.
Edited by xd_1771 - 11/9/12 at 12:19pm