It looks as if computers in my range, which would be the low end of high performance, have dual quad-core Opterons and by default have 4 GB memory. I might go for more memory, because in my font hobby I work with very large pixmap images. [Update: damn right, I’m going to get 8 GB.] I'd probably have them set up dual boot between Windows and Ubuntu GNU/Linux, with the intention to replace the Ubuntu with Gentoo or Exherbo. Basically I would be paying someone to set up the dual booting and pre-configure some things; though I’m not sure whether the pre-configuring of Windows will do much towards running it as a virtual guest of the Linux OS. Keep in mind, also, that 64-bit is more memory hungry than 32-bit, and that running virtual systems means each needs its own memory.
Maybe I would get MS Office this time, just for the hell of it. [Update: Not likely.]
I need a bigger monitor, too.
Currently I have a very old Athlon64 with 2 GB RAM. This is from before hardware virtualization support, and this old CPU also does not support instructions used in binary slaveware these days, such as Adobe Flash. (Software workarounds included in the Gentoo ebuild for Flash seem not to work, so I am using 32-bit Flash and a 64-bit plugin wrapper.)
Buying computers is very anxiety-provoking for me. What graphics processor to get is another difficult issue. I don't game, but do stress the GPU somewhat these days, regardless.