hy i have core 2 duo e7300 with hd 6670 and 4gb ram and im planing to play bf4 on 1440x900.
will i see any boost in game if i upgrade to e8400 or q6600???
Very doubtful, you'd probably do better to switch up to a haswell i3 instead. That and get beefy video card that's more geared for high end gaming instead of low power usage.