I've upgraded five more computers to gigabit ethernet, including Heavy.
The problem with Heavy was that the three PCI slots were all being used by sata controller cards. I put a gigabit ethernet on a USB port, but that's not as good as a card inside the box. My plan was to get a sata controller card that would handle 8 or even 12 drives, and I've ordered that. But I had a thought today.
Some of the motherboards I have, include five PCI slots. So I swapped the motherboard for one of those. The five slots have: video card, three sata cards, gigabit ethernet card. So it took an hour or so, but it all works, and now I have gigabit on most of the computers that I think will benefit from it.
I've ordered five more gigabit cards; they're only £4 each.