Go with Crucial, (www.crucial.com) which is a division of Micron. These guys were part of the development of the DDR2 standard, and make modules which comply with the standards, exactly, and are compatible. I consulted for them on the original DDR memory module standard, and trained their engineers. They've gone on to develop some excellent products and are good friends.
You want memory that is totally compatible with your system. Mushkin is a bit player in the market.