well, Athlon 64's are not bottlenecked by DDR1. they have an onboard memory controller, so they still get high memory bandwith against Intel's with DDR2.
DDR2 is currently only used on Intel socket 775 systems, however AMD are making a new socket called M2 which will support DDR2.
DDR2 Intel systems do not really have much against Athlon 64's with DDR1. the RAM itself has high speeds, but it has to go through a motherboard memory controller to get to the CPU. Athlon 64's communicate to RAM directly, so the difference is so far negligible.
although it will be a different story when AMD does bring out M2. their onboard memory controller will make much more use of DDR2 than Intel socket 775 systems.