I see that the newer motherboards now come with both a VGA and DVI outputs. Granted, I know they will not be as good as a separate card, but if building a machine strictly for trading (and not video viewing/gaming) can I hook up monitors to both output jacks or only one or the other?
Cannot generalize. Depends on the makes of the motherboard. Probably need to read the specs or direct the question to their tech support. And I would not say the onboard video is "not as good" as separate video cards. There is no ground for that. Again, depends on the makes and models. For trading - displaying 2D price charts... wouldn't make much difference no matter what video cards you use.