Thank you. I have a 450W Enermax Power Supply.
So it sounds like if I just go up to 256MB of RAM then that should be enough of an increase. I also imagine the faster bus and clock speeds on newer graphics cards should make a difference for me since my existing card is rather old in terms of specs.
In regards to the other cards you suggested, a friend said to be careful as some of them may either have compatibility problems with my main board or apparently some, even though they have very high resolution display limits, cannot display monitors at certain specific resolutions.
In my case I would need the first DVI port to be able to display at 1680x1050 for the Apple monitor and the second DVI port to be able to display the Dell monitor at 1200x1920. I am not sure though if there is any way to check those specs on a card first before buying it.
P.S. There is no reason for me to want to convert a DVI signal to VGA since that would only reduce a digital signal to analog and resduce signal quality. Since both of my monitors are DVI capable it isn't a problem anyway and why I want to upgrade to a graphcis card with 2 DVI ports.