Can this combo plus 8 gb of ram play modern games like crysis 3, bf4, nfs rivalsand gta v when it comes at ultra high graphics??
ultra high? not unless you are playing at a low resolution. anything more would need a $600-$700 gpu. you'll be looking at medium to high settings. you might get better but i won't give you false hope.
But i have seen videos on youtube where they play games listed here at ultra setting with r9 270x.how do they manage to do so???
i would be very, very suspicious if they are claiming 60 fps @1080 ultra on either crysis 3 or BF4. a rule of thumb is to spend about twice as much for the gpu as you do for the cpu since most games are gpu bound.
you'll get much better performance going with a FX 6300 and R9 280(x) than a 8320 with a R9 270x.