Distro for AMD64
 

1. What distro(s) are good on an AMD64?

2. How well would a 32-bit distro work on it?

Well, if you want a specifically AMD64 optimized distro, I would reccomend Gentoo, but then of course you would also need the patience of a saint... But anyway the easiest bet would be to get your favorite distro and recompile the kernel for AMD64. That should take care of the core OS. You could then recompile whatever packages need the best performace for AMD64.

Gentoo, Mandrake, SuSE, and Red Hat have AMD64 versions are far as I know. With Gentoo having the best maturity so far.

What diference is betwen an AMD64 and a single 32 bit?

32 bit will work fine.Used Gentoo and tried to use mdk with 64 bit.No luck at all with mdk.Gentoo is on the tricky side since a lot of things don't work with 64bit yet.You can get a kde (or gnome?) environment up and running no problem but if you need apps that don't work with 64 bit it gets slightly more complicated to install 32 bit compiled apps on a 64 bit OS.