They should help.....with the caveat that the older the hardware, the less return you see. If you are talking about just a generation or so old tech, then you'll see some time savings. If they are older chips, like a P2, then they -might- work....but you could find them chewing on one tile while your main system grinds its way through have the image. What will help is plenty of memory, and stripping all the peripheral out of the renderboxes. No sound card; the driver can slow the OS down, and thus the rendercow. And if you have an on board video chip, then pull any video card that might be there; you only need very basic desktop imaging for a remote box, and that will save you power on an overpowered video card, and offload the more complex video driver.