After being able to boot into a real distro, I decided to see if I could get networking booting. The kernel did end up finding the AMD PCNet32-chip inside the WT300, but it couldn't send or receive any bytes through it. Looking around in the /proc-directory revealed that the interrupt allocated for the chip didn't fire. That basically meant the PCI-interrupt was routed wrongly, which ended up as being a BIOS-problem: the PCI IRQ-routing-tables of the device I based my LinuBIOS-config on had its interruptlines routed differently from my board.
Trying to find out what's wrong, I ended up measuring some pins with my multimeter, and that's where I must have done something wrong: the next time I turned on the WT300, the networkchip wasn't detected anymore: I seemingly had blown it up.
Deciding I had invested too much time in the project to let it go now, I got online and surfed to Ebay, Marktplaats and other sites to see if I could retrieve another one. I found someone offering 21 units, and to make a long story short: other people I knew seemed interested in such an unit too, so I bought them all for a really low price. That meant I had some units to spend, and that's when I decided to realize something I always have wanted to do: make a cluster of computers which could compute stuff together.