Since the documentation doesn't mention it, may I ask what the USB connection is for? I'm guessing that it's a power source for the adaptor. Wow, not cheap adaptors but if it works it'll be worth it.

Thanks for the quick reply with info and links! So those take care of two monitors, and my third is connected directly to one of the DVI ports on my video card. If you don't have exactly those adapters, it's not going to work. Based on my system, which is a little newer than yours based on what you have listed in your profile, this is the magic documentation: