MilSim :
An i3? Im no PC genius but will this be able to keep up with most games with alot happening at once?
Despite what some ill-informed people believe, no, it's actually perfectly fine for most games. Physics in most games is still single threaded, so the above GTAV example is actually going to be FASTER on the 6300 than on a i5 6400. The issue is going to be in AI/script heavy games (think starcraft), but for your budget you'll have to pick one of two options:
1) Stable framerates but lower graphics settings (replace the i3 with an i7 6700 and the 1070 with a 1060)
2) Higher graphics settings but less stability in some games (as-is)
And Hawkshot overshot the price target, he forgot to put an OS in the system and left zero cash for keyboard and mouse!!!!! Your budget just isn't high enough for a 6600K, and in most games the i3 6300 will outperform the i5 6400 and 6500.