Dual Channel Memory Athlon 64

the only dual channel athlon 64 solution out right now are the opterons and FX's and those require registered memory. the performance difference between a FX and a 3400+ arent really worth the money.

socket 754 boards are all single channel memory so it shouldnt matter whether you go with 1 stick or 2.

the upcoming socket 939 will support dual channel, non registered memory.

500 Mhz DDR will be a waste of money at this time. Athlon 64s support up to DDR400 right now and the memory controller is on chip, not on the motherboard. So unless AMD adds support for PC4000 memory in their next run of Athlon 64s you will not be using the full performance of your memory. DDR2 is also on the horizon so I am not sure how relevant it will be to try to future proof by buying more expensive memory now. my advice would be to just to stick with DDR400