G3220 vs Core i3: If the idle power consumption is very very close, I rater go for the i3.
The cost is not so much more if I see to the total build cost for everything, and there is more power if one day needed, the aim is a low idle power.
I´m going to take a look at the Mobo from MSI and INTEL.
Personally i think the Pentium is enough for HTPC and server, its 3.0ghz dual core, its very capable, its missing some cache, hyperthreading, lower iGPU (still enough for standard 1080p playback) and some other small things. Now if you want to go for i3 its fine, i just feel unless you need it its not worth the extra $50 (i would spend this on a better PSU, cpu cooler, case or even better fans). Now in line with your thinking, you could even go with Quad, and have more cpu power for the future, specially if you might use in the future for encoding or transcoding to multiple mobile devices, etc (im still recommending the Pentium though).
Check this thread, DH77DF vs DH77EB - power consumption
, from Kappa7 post,
I've build the mini pc with these components:
Ram: 2x4GB Corsair Vengeance Low Profile White, 1.35V @1600Mhz 9-9-9-24
SSD: Plextor M3 128GB
Power supply: MeanWell GS90A12-P1M + pico psu 90-XLP
Fan: Intel stock fan + Arctic Cooling F8-PWM on the case.
OS: windows 7 ultimate x64
I've disabled the Turbo mode of the core I5 to limit the maximum power consumption under load and I've activated all the C-states. I've also set the power policy in the bios on low power and I've checked in windows device manager the box that says "Allow the computer to turn off this device to save power" on the firewire controller.
I've measured a power consumption under load (with prime95 + furmark) of 72W (about 80W with the turbo activated).
The idle power consumption, when the fans are connected, is measured with the minimum allowed rotation speed (it's more than enough keep cool the system @idle). The minimum rotation speed of the stock intel fan is 1000rpm and the artic cooling fan is 350rpm. No keyboard nor mouse are connected during the tests.
Here the results:
With gigabit connected, video output enabled, fan processor connected, fan case connected: 11W
With gigabit connected, no video output, fan processor connected, fan case connected: 9.8W
With gigabit connected, no video output, fan processor connected, fan case disconnected: 9.6W
With gigabit connected, no video output, fan processor disconnected, fan case disconnected:8.8W
Pretty impressive if you ask me, below 10W idle on a Ivy Bridge i5 quad, given that its headless and with very little enabled, and with picoPSU, but still impressive none the less. Most of us that have look into building a very efficient PC, have found the best results on Intel mobos, you lose all the tweakability of what aftermarket boards have, but they are very nice on their own.
As final suggestion, try to get an efficient PSU, if you can platinum or gold, Corsair RM are looking nice with a huge offering on Watts and not so expensive.