Each set comes in a cardboard case with an install CD and a live CD. I popped in the live CD from the AMD64 set and rebooted. After a bit of text-mode configuration (language, keyboard layout, etc.), it booted up X11 with my devices mostly configured.
I have never gotten sound to work on Linux before. Just when it was finally becoming stable on x86, I moved to AMD64, where it's still not very well supported. So you can imagine my surprise and pleasure at this discovery.
It didn't realize that I had two monitors, but that wasn't surprising—it really had no way of knowing. A quick search of the Ubuntu wiki turned up instructions on how to configure it; I edited my xorg.conf, crashed the X server (the Linux equivalent of Ctrl-Alt-Del, except it just drops you to a command line instead of rebooting) and restarted it. It needed a tiny adjustment to make it properly understand the way my monitors are oriented, but that was pretty simple. Another thing I'd strugged with on my previous installations was easy as pie here. (To be fair, this is probably more a reflection of advances in X.org than Ubuntu itself, but it was still a pleasant surprise.)
Basically, everything just worked. Even GNOME wasn't that painful, despite my previous experiences with it. I may end up installing this thing alongside Windows. (The server will continue running Gentoo—I still maintain that there's no better distribution for a server.)