Well, if it turns out that the mobo in this WinXP box is going down, I might opt to buy the Mac versions of all the apps I need, and not buy another Windows box, just use the Mac.
That’s my video system, though, and there are disadvantages to having a dual use machine.
I doubt I will build another computer, though. I might just buy a Dell pre-built (w/ XP, not Vista) to replace this one . . . . if it needs to be replaced. We’re not there yet.
Not guaranteeing it'll fit your needs, but with that many cores and that much memory you can probably afford to run XP in VMWare Fusion or Parallels.