You are indeed correct, it doesn't matter.
Any vaguely current discrete video card is powerful enough to handle three monitors of 2D applications but only certain ATI/AMD cards have the hardware necessary to connect 3 and you need the adapter I linked to do so.
There are some specialty cards that can handle 3(or more) but they are overpriced. For example here is an HD4350 that can handle 4 monitors;http://www.newegg.com/Product/Product.aspx?Item=N82E16814139055
The HD5670 is many times more powerful than that card however. Basically, when it isn't HD video, 2D is trivial for modern cards.