Hello Project,
The answer to your question would be based on your application and your budget. This choice, among other things, greatly depends on the motherboard. Let us be clear with a few things regarding the A64. First, RAW memory clock always increaeses performance, however in the race between tight timings and raw frequency, sucka and others have clearly shown that 300MHz (2.5-3-3-x) > 260MHz (2-2-2-x). This us brings us to the question if your board is capable of doing high HTT.
I don't know much about your board, but since its not very popular, I'd say NO.
Based on this, one could say that tight timings would be the best option for you. Fine, we have tight timings and at what HTT? If you are limited to < 250MHz, I would pick a 2Gb kit and clock it to the max. Crucial seem to have the best 2Gb kits thus far. Other choices could be OCZ and Mushkin. Note that these modules are a bit pricey. Also, motherboard compatibility needs to be looked at. <I have no data about this>
If price is a pinch and you board supports high voltages, get anything with the BH die i.e OCZ VX, Patriot xtreme or Mushkin redlines.
In the event of you chossing 512 X2 Mb, I don't think TCCD would be the best choice (although patriot xblk pc3200 is very cheap these days).
Guten Tag!
S-N