@Darrin
if you already own a CV3D and a Deneb I think you are well served.
If you really want to use very high resolutions like 1920x1200 with lots of colours and use lots of screens and notice a lot of lag when switching screens then a Mediator4000 may come handy if you fit a Voodoo3 or -even better if you don't use Warp3D- a Radeon.
If you use a small monitor with screensizes of 1280x1024 or lower a CV3D could be enough.
The only point I don't like about PCI solutions is that there are not high-quality automatic monitor switchers. Switching using an electronic monitor switcher is not as bad but automatic switching is soooo comfortable :-)