I wouldn't say DDR2-667 RAM overclocks to DDR2-800 speeds easily. Not all modules will go that far (it's a 67 Mhz overclock from 333Mhz, so around 20%).
King$nake: the RAM speed is not important with your motherboard, since it probably supports DDR2-533, DDR2-667 and DDR2-800 (with DDR2-675 being a variation of DDR2-667).
However, as I understand it, you already have DDR2-667 (675) RAM installed. There's no point in installing faster DDR2-800 RAM because it will downclock to match the slowest module installed.
Just get DDR-667 RAM, it should work fine.
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