Saw this device coming out. http://www.gefen.com/kvm/product.jsp?prod_id=4517. Could this be used to run a DVI monitor as a client monitor out of Xpress Pro/MC? I'm running a single processor G5 1.8 Mhz with an upgraded Radeon 9800 card with 256MB. I though about popping the Radeon 9200 into a PCIx slot to achieve a client monitor, but might this be a good solution for a similar price?

Nope.  First off it's for Windows with OSX support coming "soon".  

Second, if you want to use any DVI monitor as a Client monitor you have to use the AGP port as it's the only port the Avid will use for moving pictures.

Third, your single processor G5 isn't going to run the next version of MC (see the pinned post at the top of the forum page) so any PCI-x cards won't be compatible with newer Macs.

Better to use the 2nd graphics card to drive the bin monitor with the caveat that it's got a limited lifetime.