? about running cards in SLI

I'll be getting a new computer soon and a have a EVGA GTX 260 going in it. If I were to get another GTX 260, would I have to get another EVGA one or could I use a different brand (like PNY, BFG, etc...)? I would like to get another EVGA one because I trust them, but if I were to find a great deal from another brand, I might get it. Also, would the clock speeds of everything have to be the same or would the same thing happen that does with RAM (it just goes with the slower speed)? Thanks for any help.? about running cards in SLI
SLI will work regardless of brand. Also, if there are differences in the stock clocks, the higher one will automatically lower to the lower one, so it will work fine. Just make sure you have a quality PSU to run those in SLI ;)