its always worth investing in branded quality memory; but I'm not sure if paying twice the price for ultra low latency ram is worth it though. Firingsquad's test even showed that when the modules where ran at PC1600 speeds, the performance drop was relatively marginal, so I wouldnt worry too much about it.
Other things I'd keep an eye on is Cool & Quiet. Not all motherboards support this yet, though that should be a matter of bios revisions. more importantly, not all athlon 64's support this; see <A HREF="http://www.xbitlabs.com/articles/cpu/display/athlon64-3200_5.html" target="_new">this page</A>. Might as well pick a cpu that handles this.
Are you going for a nForce3 or VIA board ? Anyway, good luck with your new powerhouse !
= The views stated herein are my personal views, and not necessarily the views of my wife. =