Not much point to that, you would have 4 independent GPUs.
Yep! Outside of running them independently, you are running into diminishing returns past a two-way SLI. Adding that third or fourth GPU doesn't see nearly the gains as adding that second GPU (in a SLI configuration). If you need more muscle than a pair of GTX 680s, then sell them and upgrade to a pair of 980s.
Do you have a motherboard that supports quad or tri-SLI, usually pretty pricey and need a PLX chip. Nvidia doesn't support SLI at anything less then 8x per card.
Not much point to that, you would have 4 independent GPUs.
Yep! Outside of running them independently, you are running into diminishing returns past a two-way SLI. Adding that third or fourth GPU doesn't see nearly the gains as adding that second GPU (in a SLI configuration). If you need more muscle than a pair of GTX 680s, then sell them and upgrade to a pair of 980s.