Now that I think about it, it seems to me that you're aiming for something as future-proof as possible. Well, I'm not sure how cheap you'll get if you want to go all out in that regard, but it looks to me like the major trends that impact this are the AMD socket 939 processors (if you go AMD), and PCI Express. Again, those things will probably set you back a bit of dough, but I saw you were possibly going for 64-bit processors with those mobos, but they support the type of chip that AMD isn't thinking of sticking with.

PCI Express appears, at the moment, to be the next big thing. It's intended to replace both AGP and PCI, while being backwards compatible with regular PCI. It has a much higher bandwidth, and there are already a number of video cards out there for it. However, it looks like it's mostly an Intel thing for the moment, so you might not want to bother. I think for a year or two it'll be mostly video cards taking advantage of it. I'm planning on a new system, and I'm not thinking about PCI Express.

Anyway, those were just some things I was thinking about. I'm probably completely wrong, too. It's hard to get info on some of these things. I don't know, maybe it's just me, but there seems to be very little info out there on the current state of 64-bit processors. I've had to sort of piece together my own understanding of it. Please correct me if my interpretations are wrong.

*edit*
by the way, if you've thinking of the CPU you linked in that post even though it's a 32-bit (it's still a very nice CPU), then I heartily recommend the Asus A7N8X. It's my current mobo and I think it's fantastic. SATA, two LAN ports, 4 rear USB 2.0 ports (and pins for two more), and it's been very reliable. It's also good as far as not being awkward to work on. There aren't really any poorly placed connectors which can make it frustrating.