I would assume the only reason you would need a card would be to bring in media at different resolutions other than the native. Hell, if Xpress Pro would handle 2:1, that would be all you would need.
I online in 2:1 except for graphics which are 1:1. Our offline guys work in DV25. Right now DV25 and 1:1 are the only resolutions that Xpress Pro does.