Just get 2x512 value PC3200 from Corsair or Mushkin--you'll want this for your Barton running at 200 FSB anyway. If you plan to do heavy overclocking on your A64 and want to run 1:1, look for some cheap stuff using TCCD chips (Patriot CL2 PC3200 and G.skill PC4400 come to mind, but you'd have to spend a bit more). Running a divider on the A64 probably would be OK, though.