The cas level matters for athlon64s, as does the command rate (1t vs. 2t). The other memory settings are not as important as the FSB, which is what I think those memory latency articles were trying to say. If your memory won't run fast latencies at stock FSB, they won't run at all at higher FSB.
I've done some testing on my own a64 rig and there are definate benefits to running cas 2 or 2.5 vs. cas 3. The really hot rigs are running TCCD chip based memory and they're getting cas2 or 2.5 well up past 250mhz fsb if you set the voltage up high enough. Some companies are even selling voltage boosters that plug into an empty ram slot and boost the memory voltage waaay up. That's far too much effort for me, but I'm convinced that there are benefits to getting quality memory instead of the cheap stuff, both in performance and reliability. And if you're going to overclock, you just can't be putting crap into the mix or you'll get crap for results right back out.
Decent cas2 (or 2.5) PC3200 or cas 2.5/(or 3) PC4000 is what you really want. No-name cas3 PC3200 is probably rebadged pc2100. You should be able to get that stuff without spending much. Crucial sells 512 meg sticks of cas 2.5 pc3200 for about $89, not much more than the crappy 2700 and slow 3200 stuff you get in the bargain bin. And crucial will cross-ship you a replacement stick if it ever goes bad. You won't get that from no-name retailers. Want proof? Go to Fry's and get a handful of their sale memory, any speed you like. Put it in your computer, let it autodetect at it's "correct" speed, and run memcheck86 on it for a few hours. I've done just that in the past, and I went through 6 sticks before I found one that was good. I needed two, so I returned them all and had crucial send me some overnight. Both the crucial sticks are still running faster than spec 4 years later, without errors.
That's what you get with quality memory, same as any other quality parts. Speed and reliability.
