Confused about 64-bit architectures.

[Adam Funk <a24061@yahoo.com>]

I'm planning to buy a new home computer soon and am considering Xeon,
Athlon 64 and Opteron 64, but I'm not sure about the relevant Debian
architectures, ia64 and amd64.  Which one applies to which of those
processors?

I'm also concerned about the potential shortage of 64-bit software for
a general-purpose workstation, so I'd like to know what other people
think of this.  Will I be setting myself up for a lot of hassle?
Should I just stick with a Pentium 4 for now?

Thanks,
Adam