You have to pay attention to a few components. So - fullsize case where a big 3-fan, 13" card won't run into the hard drive or DVD drive cables, if you choose

You have to pay attention to a few components. So - fullsize case where a big 3-fan, 13" card won't run into the hard drive or DVD drive cables, if you choose to go that route (it seems to be easier to have multiple Founders edition cards than multiple OEM's, cooling-wise). - for 2 or 3 fan OEM cards, you have to be moving a lot of air thru the case - X99 /Z170 / Z97 motherboard (X99 has the highest allocation of PCI-e3 lanes to 2 or more GPU cards, and newegg does a good job of standardizing how they report lane allocations) - and a beefy powersupply, 750+ watts and a bunch of PCI-e 6 or 8 pin connectors, and you shouldn't hit any constraints. Also i recommend "Cuda for Engineers" by Storti /Yurtoglu as a good first cuda book, and the Wrox Pro C Cuda programming as 2nd book. There's another that just came out, Programming Massively Parallel Processors, Third Edition by Kirk /Hwu, that looks good but i haven't read it