But, as you say you wanna them for gaming, you should take a look at the new Sapphire 7950 Flex-Edition, which allows you to connect up to three screens without using active adapters..
So, having this girls in CrossFire may allow you to set up that amount of screens..
When the cards are CrossFired you can only use the outputs from the first card.
@ LexLuthor
CrossFire definitely only allows you to use the outputs from one card.
Non-CrossFired each card can use whatever outputs it's capable off.