Bogie -
Be sure your router is up to the traffic demands if you'll be doing large format printing over the network. The typical Linksys/DLink style SOHO router doesn't like sustained heavy loads; overheating is common. I've already spoken to a couple of shops from this board that were having trouble with this very issue.
PMG -
As was stated before, that device is only USB 1.1. However, does your equipment require USB 2.0? You'd be surprised at how many peripherals don't use 2.0.
Also note that this doesn't let you run your printer over the network. It just lets you use Cat5 cable to extend the wiring. It's still convienent, not overly-espensive, and if your stuff works without USB 2.0 it may be the ticket.
Re. wired USB extensions -
See if you can test the extension before buying. Some devices (luckily, most printers and plotters) work fine on an extension. Others, especially hard drive adapters, won't work on an extension.