I highly doubt you'll get 1T with 4GB of memory. If you're looking for 1T on a 2x1GB set, I'd get these: 2x1GB Team DDR2 667 3-3-3-8-1T
Guaranteed Micron D9GMH, and will definitely do 1T at 667. They have as good a chance as any at keeping the 1T up to DDR2 800, but no guarantees. With an 8-layer PCB, you can probably give them up to 2.35v without too much worrying. At that voltage you have a very good chance of 1T at DDR2 800.