wow stupid question but yo can put two video cards?
depends if you're using Nvidia or AMD, Nvidia doesnt support more 3+ way sli anymore but amd still supports Crossfire for as much graphic cards as you want, but if you are going to have 2 or more graphic's cards, they are going to have to be exactly the same
You can also pair an apu (cpu + bit of a gpu, similar to intels approach to onboard graphics) with a gpu. Great if you are broke af and can only afford a little bit at a time. We aren't all @Copperhorse