drdeadkin :
So i have g.skill under clocked to 2400 its normal freq is 3466, if i get a different brand like cosair at 2400 for example will it cause any problems because i do not want to spend 100$ on 8gb of ram. Or i can buy the same brand but different base frequency.
It won't "cause problems" but theres a chance it won't work. Chances of it working are higher if both are the same brand, but theres still a chance it won't work. In reality you could buy another set of the exact same kit you have now and it won't work due to the chips they use.
So in summary, if you must, at least get the same brand, that will have more of a chance of working.