So currently I have a GTX 560 (1gb) GPU in my rig and I would like to increase my GPU crunching power.

But first to clarify, adding an additional GPU will increase my computers GPU crunching speed/ability correct? As in will I be able to run say for example, two GPUGRID tasks simultaneously? Or are the cards seen as one super card that just computes tasks faster?

If an additional card will increase my GPU crunching capabilities, I will probably end up getting another of the same card, to keep the option for SLI capabilities open. But out of curiosity can you run two different cards effectively?

Thanks for any input, my current research hasn't turned up much!