I wouldnt buy a pentium g mate,full stop
Its a hobbyist chip for overclockers ,not a serious gaming chip.
I understand the talk of upgrade paths etc but seriously I havent seen a game in the last 12 months that will not take advantage of 4 cores (apart from stuff based on the arma engine) - if you cant afford at least an i3 ,then go amd .
& seriously for an matx build stick with the n200 I listed ,its head & shoulders above any other budget matx case on the market (& it comes with decent preinstalled cooling)
FM2+ is good for HTPC's and entry level gaming on a machine you don't plan on upgrading much. The socket is the one of the worst possible choices if you want any upgrade path. The 860K is the best CPU available in that socket and it's roughly equivalent to an FX 4300.
1150 will give you the longest possible upgrade path, AM3+ is good if you plan on overclocking. If you have a large budget, 2011 will give you quad channel memory.