The 8600's board can be replaced with a Kansas board from a 9600, taking a G3 daughter card (soldered or ZIF) and giving you six PCI slots (but losing the AV). As BC wrote, you can make an 8600 into an even more accomplished machine than it started as. Mine runs 9.2.2, with a G3 at 400MHz, shortly to become 450MHz, and feeds 45GB of Ultra-SCSI HDDs. It can take up to 1GB of 168-pin EDO (cheaper than FPM) RAM.

de