Any Double head nvidia card will support dual monitors. So will their software that runs the nvidia card.
Take note though. Any time you run a second monitor you are going to split the available video processing power in half almost exactly.
Or if you run 2 independent cards your computer will split the bus in half to support each card. (which does almost the same thing in terms of speed)
example: If you have a 2 slot SLI slot motherboard and a SLI bus of 16, each card will take 8.
That only way around this seems to be to have 2 different generation cards but then you run into the problem that the older generation card can't keep up with the newer card. Assuming the machine even has the slots to run 2 different generation cards.
That is about as simple as I can say it.
This IS Not all doom and gloom. When you start trying to run double monitors the best solution is to get high quality card(s). So the drop in power for each monitor is noticed alot less.
Most of this is false.
First of all almost any recent video card (that has dual out puts which most do) from the lowest to the highest will support dual monitors whether it's from Nvidia or ATI. For 2d apps, which i'm guessing the OP uses most as he doesn't already have a dedicated card you won't notice any performance issues with 2 monitors over 1.
Whether the bus speed gets cut using dual cards is dependent on the chipset of your motherboard. And even if you run at 8x and 8x you won't see much if any loss of power as very few cards (ie only the very top of the line) come anywhere near using the available bandwidth.
And with 2 cards for 2 monitors it makes no difference if they are the same generation. In fact in xp (vista won't allow it though) you can even run an nvidia and an ati together. The only time the type of cards mixed together matter is if you are running dual cards for 1 monitor (as in SLI or Crossfire).
If you need a card for basic 2d apps it would be an utter waste to but a highend or even midrange card just for 2 monitors.
To the OP,
Something like this would do fine for you
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121259.
It has VGA, DVI and HDMI out to hook up you monitor and tv to. It does have a passive heatsink so no extra noise in the case as well but if your case doesn't have decent air flow you may need one with a fan on it.