Two monitors - two adapter cards or one?

I'm looking to hook up 2 monitors for day trading. My setup:

- Dell 531
- Vista SP1
- AMD Athlon(tm) 64 X2 Dual Core Processor 5600+ 2.80 GHz
- 2GB memory
- NVIDIA GeForce 6150SE nForce 430

The video card sucks; can't even display multiple charts from E*Trade software. So I either need to upgrade it to one with 2 ports, or buy 2 cards.

Which option should I pursue and what card(s) are recommended?

Thanks, geoff

 

If all you need to display is charts, this will do fine:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102724