I never used a matrox box, and the reason is that your secondary graphic port needs to support a 2x width of the resolution of your external monitors, in order to stretch the picture properly. All it does is just to split the image in two. At least this is how I understand it. Hence if you want to run two 1920x1200 screens, your graphic card needs to support 3840x1200. Most likely your laptop doesn't. I'm not sure how the picture will look unless you have this pixel-match on the resolutions. Someone who have the matrox box may comment on that.. ?
I've been looking for a dual external laptop setup myself, and now I will try out the Tritton See2 Xtreme, as linked above. There is a potential lag issue on this though, and I don't think video will display well, or at all. But should work for trading applications I think.
However, if you buy a new laptop there are some with dual video ports. DVI and HDMI for example. However you need to confirm if they are actually able to run simultanously separate desktops.
The Tritton is a very light-weight solution. Giving you two external video ports, including the built-in external of your laptop. However to get full performance you need either a dock with graphic card, or a laptop with built in dual support. The latter can be very difficult to confirm though, both by searching the net or by asking any support person.
