it should be exactly the same model on the same chips (little modules on PCB) and it would be perfect to get them from the same production stream which is pretty much impossible after you're buying 2nd stick after a while.
I heaven't heard about 'best ram' but from my expierienc dual channel usually works with Kingston KVR memories even if you're getting 2nd stick after a while.
Anyways even if dual channel won't work you'll loose just a few percent on overall computing power of your PC.
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