In a few weeks I'm going to buy a gpu for my pc ( i5 4440, 8gb RAM) . I have a budget for a r9 270. my question : it is any difference ( fps, temp, noise) between the 270 and 270x, both overclocked ( without tweaking the voltage) and what manufacture ( msi, gigabye, asus and maybe sapphire, which have only 2 years warranty)?