I use the same driver as you so driver should be fine and I'm positive that you will not need a dummy plug.
cgminer should give the best performance. You can write the config for all of the cards in one file or you can use GUIMiner since it is easier to use.
but my computer just ricieve 3 gpus..i tried to used win 8 but it's the same..1 card error code 43..i don;t know how to fix it..