Looking at this the interface is PCI- Express:
http://uk.insight.com/en-gb/productinfo/graphics-cards/PNYOG290B
This is the most common current interface.
Questions to ask are will the case fit a full height graphics card, or a just a slim one like the picture in the link.
Next question is do you need passive cooling (ie no fan noise?) Most graphics cards have a fan on and are optimised for 3D power.
For your purposes the card should not be taxed too much.
There are two main brands of processor: NVIDIA and AMD (was ATI).
Focus on the chip code and memory, and you will see that rival brands (Saphire, XFX etc) sell essentially the same graphics card but with their twist on it. I tend to buy AMD cards, but there is no reason beyond loyalty for this.
Lastly, what interfaces do you want for the monitors? DVI, VGA, HDMI?
Different cards have different ports.
There are some great cards out there for £40-50.
I tend to buy ones in the £90-£140 bracket, but then thats because the kids use them for gaming.