There is actually a large difference between 3 and 3+.
If you want to run 3 monitors then get this Sapphire 6450
. It will let you run three monitors without any Display port adapters.
If you want to run more than three monitors then I would suggest getting two of the above linked video card.
Importantly, this video card will not be able to play any games. It is only suitable for running office applications.
Here is an AMD FAQ