There are 3400+ socket 939 chips. They are sold in mobo/CPU bundles only.
And it is true that super expensive RAM is far less important on A64 platforms than intel. I recall reading a thread on HardOCP where the fella showed through various benchies that theres virtually no difference between mem timings/RAM speed when using A64 CPUs. Hell, PC2700 timings only made a differnece of a few FPS in real-life gaming situations. It does become important, however, where pure bandwidth alone makes a difference - like in mem bandwidth benchmarks. If you are dying to upgrade you may not want to buy really low latency stuff. The cost to performance ratio is too high to justify it.
I'll post the link if I can ever find it again.