the reason that 2 sticks of
Ram are better than one is the Dual channel factor..One stick you only get one channel..Two sticks you get double the bandwidth..ie pc400 needs 2 sticks to run @ 400mgz if you only run one you only get 200mgz..
And yes you should match
ram but its not a nesesesity to get the same brand, but some motherboards like the same brand
ram..
As you run into problems with the timings of the
ram etc.