depends on the resolution of the monitors. 3 x 1080p monitors would work as long as your not looking for ultra high settings in game. Here's a YouTube video using multi monitors AMD Radeon RX480 8GB GDDR5 Eyefinity test - Not to shabby! - YouTube It can run gta v at 5760x1080 with a combination of high and medium settings. Gamers comment not mine.
If you going for an aftermarket card go for an 8GB ASUS, MSI, or XFX card.
the RX480 would be a good stopgap before investing in more expensive graphics cards, FuryX cards would be my first choice if it wasn't for the price and 4GB vram and what's coming next year.