A while ago I remember reading that to achieve a resolution of 5040x1050, you would need an extra DVI cable in addition to the normal setup. Is this still correct?
I think it was a dual-link DVI - Analogue cable of some sort.
Assuming you have TH2GO Digital Edition you will have received a short DVI cable in the box that goes between the video card and the TH2GO. If they didn't already come with your monitors you will need 3 x DVI dual-link cables to go from the TH2GO to each of the monitors.
If you have a later model Nvidia card (mine is a GTX480) and if you monitors can handle 50hz you should be able to achieve 5760x1080 (3 x 1920x1080) with the latest Nvidia driver and TH2GO firmware.
There is a TH2GO firmware update coming soon that will address the bezel management issue along with other issues.