I was just on the MicroSpot web site and saw that they are selling a bundle for the HP 500 series. Perhaps that is what you need?
We use a DesignJet 488CA here and have had some complaints about the manner in which the HP Software RIP on the host computer. When the PostScript job leaves the client running VectorWorks 8.5.2, the Software RIP (also on a B&W G3) doesn't detect the file and begin the RIP process unless the Finder is made active. Unless you have a dedicated host, that means interrupting the user of the host computer to switch in and out of the Finder. Then, the Software RIP can really only handle two jobs at a time even though we have tried some really high memory allotments to the software. Five jobs may be queued up, but then you have to go and Quit the RIP, re-launch it and print two more jobs. Again, not fatal, but pretty hands on to keep the workflow moving.
I'm not sure if the RIP set-up will be different for your planned 500 series purchase, but those are the caveats I give. Perhaps MicroSpot is worth keeping around(?)
-Dan Rafferty
Ryall Porter Architects
drafferty@ryallporter.com