for that budget you should look at getting second hand parts and future proofing rather than tryna build a good new rig...this is basicaly my rig.
2nd hand amd 955be (approx R700)
asus m5a97 evo(approx R1500) (around R1200 2nd hand)
4gb ram(approx R300) (shd be 2x2gb.cheaper 2nd hand)
amd 7850(approx R2700) (around R2300 2nd hand)
23" led screen(approx R1700) (around R1300 2nd hand)
corsair gs800(approx R1200) (around R1000 2nd hand)
new(blown budget or horrible compromises)
2nd hand(R6800+case,keyboard and mouse) and most of the parts should last 2 years without impacting on your graphics too much.
basically i run bf3 on almost the highest graphics(after a little overclocking)and im able to put in a second 7850 when i have the money and any amd cpu for the next 3 generations.power supply will be good for 2 of the new gen graphics cards
