Rather than buying/building a new computer I'm trying to get by upgrading what I have. The advantage of this method is that there are people out there who have spare parts I need left over from their own upgrades. I've been placing some ads on the local Freecycle and on my Multiply Market. I also advertised some of the kit I've had lying around for years that is too old to get any money for. This week I managed to get rid of a fair bit and, in exchange, I gained some useful parts. These consisted of an extra 256MB DIMM and a couple of graphics cards. The nvidia MX400 looked like a good option for my main Linux box as it's old enough to be supported by the motherboard. It may not give a huge performance leap over the on-board graphics, but it frees up some memory. The Matrox G550 will go in the Win98 box that the kids use.
I've had a few issues with the MX400. After it didn't initially get me into KDE I did some digging and found out it needed the legacy driver. I think that is working, but I now still have problems getting KDE to start consistently. I sometimes get a desktop with no toolbar or window title bars, but did once manage to get everything looking as it did previously. I need to learn more about how it all works. There are various guides that give you a series of commands to run to make something work, but they don't always explain why it works.
On the upgrade front I'm still on the look-out for a better CPU. I should be able to fit something at least 50% quicker than my 1200 Duron. That will help speed up my current project to convert some Freeview recordings to DVD format.