Many graphics cards these days "support" multi-monitor setup. Believe it or not, it typically comes down to a physical factor: the number of display ports. From there, it is more a matter of whether the graphics card can effectively run X-Plane at the wide Field Of View on a three-monitor setup. This is a great video for X-Plane 11, which will have great multi-monitor support: https://www.youtube.com/watch?v=FlhKrfoEHDs#t=145.519729571
You said you want two different card suggestions. They best bet would be to look at similarly performing cards from two different companies: Nvidia and AMD.
Nvidia: Many of their newer cards are phenomenal. SLI setups are even better (as in two of the same graphics card working together as one to yield roughly 1.5 times the graphics computing power). You want to make SURE the card you buy has 4GB of VRAM, as X-Plane has the capacity to hog it, and adding pixels (increasing resolution) and monitors adds to that. 4GB is usually the perfect amount... most people don't get more. As for the graphics card, the GTX 1060 or greater should do an amazing job with rendering at that FoV. The GTX 1060 starts at around $250, and s not SLI capable. The GTX 1070 starts between $400 and $450, and the the GTX 1080 starts at around $620. If these prices are a bit hefty, the GTX 960 (SSC) can also suffice, starting between $170 to $200. As for vendors, there are many, but I recommend NewEgg or Amazon, as the reviews are accurate and customer support is generally dependable.
AMD: The "Radeon" graphics card, as it is typically known. As usual, look for about 4GB of VRAM. Now, I personally have little experience with AMD cards, but the RX 480 is pretty comparable to the GTX 1060, starting at around $220 to $250, though the Nvidia GTX1060 is known to be small bit better:
The RX 480 is one of AMD's top performing mainstream graphics cards, to my current understanding. The GTX 1070 and GTX 1080 have higher benchmark scores, as does the GTX 1060, though it depends on your preference and price point. Judging on the hardware you purchased, I could safely guess you are willing to chip in a bit for the graphics card(s)?
*I am not affiliated with Laminar Research