Could four 1080p monitors be 4K on the cheap? Probably not… but keep reading.
Image Credit: Phoronix
Phoronix published an article for users interested in quad monitor gaming on Linux. Sure, you might think this is a bit excessive especially considering the bezel at the center of your screen. On the other hand, imagine you are playing a four player split-screen game. That would definitely get some attention. Each player would be able to tilt their screen out of the view of their opponents while only using a single computer.
In his 8-page editorial, Michael Larabel tests the official and popular open source drivers for both AMD and NVIDIA. The winner was NVIDIA's proprietary driver although the open source solution, Nouveau, seemed to fair the worst of the batch. This is the typical trade-off with NVIDIA. It was only just recent that The Green Giant opened up documentation for the other chefs in the kitchen… so these results may change soon.
If you are interested in gaming on Linux, give the article a read.