You don't need the same brand just the same timing, voltage and frequency. If your using PC6400 @800mhz with 4,4,4,12 timings you want PC6400 @800mhz with 4,4,4,12 timings. If you buy say PC5300 @667mhz with 4,4,4,12 timings all your ram will downclock to the slower PC5300 speed.