That would be 667mhz not 675 there. Many like ocing and go for the DDR2 667 memory while the fastest stock is obviously the 800. Since I planned an essentially stock build here for multimedia, video capturing/editing, and throwing in some gaming at times I simply went for the DDR2 800 performance memory with the faster timings over value or memory seeing a slower speed.
Going with a good brand is the first thing as well as price to consider. Keeping away from the cheap generic brands and planning things out by looking over some of the best brands like Corsair, Crucial, OCZ, Kinston, and others while pricing is the smart move.