I assume you are in the US?
If so this is one of the cheapest decent gaming rigs you can get. It is over budget but you get a much better price erformance ratio if you save up a bit more. PCPartPicker part list
can it run modern games on mid-high '
BF3 = High / Ultra
BF4 = High - Migh-Mid
Crysis 1 + 2 Will run well and 3 may have to run in low-mid
No idea about planetside or loadout.
DayZ / ARMA II will run in high-ish (I play DayZ in medium on my GTX 285)