The GeForce2 MX with Twinview from Nvidia is a great card but I had to put it into storage lately after upgrading to Windows 2000. They have no tech support and the drivers they claim work for Windows2000 don't work on my computer. It worked fine under WindowsMe.
Yes, 192Mb RAM is needed for each additional monitor if you want to be on the safe side. Baron's info is accurate and he gives his reasons for the high amount of RAM needed. Additional RAM is very cheap, a 256Mb chip is only about $50.