pqi POWER Series 1GB (2 x 512MB) 240-Pin DDR2 SDRAM Unbuffered DDR 533 (PC 4200)
Because its designed to run at PC4200 (250 MHz? 300 MHz?), it can 'overclock' (its underclocked to PC3200 to begin with) to that speed without a sweat. Its overclockability from there should be equal to other RAM, and your CPU will probably reach its limit first.
EDIT: The above is bogus.... its an entirely different type of RAM, sorry. It shouldn't be included... it WILL go faster then the other, but thats because its an entire different technology.
Go with the OCZ or the DDR pqi.