I was looking around for memory today, and after reading a lot of reviews from Anandtech, Xbit, consumer reviews,
max FSB(I was focusing the most on this); so much research.
I have found the best 1gb modules:
Crucial Ballistix Tracer PC4000.
They are better than the non tracer version, becasue they seem to last much longer than the regular ballstix. The funny thing is, you can no longer buy the 2 GB Kit anymore, for some reason Crucial discontiued the 2GB kit. "There is no doubt that the Crucial Ballistix 2GB bit is the best performing 2GB kit that we have ever tested."
Quote Anantech.
However, you can get 2GB of this memory very easily: Just buy two sticks.
All the sites that reviewed the kit got within 10mHz of DDR600 or higher. I believe it was Anandtech who got DDR610 out of these things.