Help build NAS/HTPC

hi ,
after reading a lot for all the last week i'm now trying to build a low power nas/htpc build:

Case:
Case Fractal Node 304 o.N. Mini ITX Link

Motherboard:
Asus P8H77-I Link

CPU:
a) Intel i3-3225 Link
or
b) Intel celeron g1610 Link

RAM
2x4gb generic ram

HDD:
2x WD Red 3TB (probably i'll buy another 2 in the next year) Link

PSU:
don't know

NO GPU


i would like this system to be low power on idle or nas usage (torrent download etc...) but with the possibility to play video using xbmc smoothly and have more power when needed.
i have a 47'' Lg TV with 3D (Lg47La640 ) Link
but i don't really need that this box will be fully 3D compatible.

-which cpu is the best for my needs ?
-do you have some advice about the psu ?
- does someone has a similar system and can post his power usage ?

sorry for my awfull english

Thank you very much.