Well, at stock speeds PC800 whips PC2700, but PC3200 whips PC800. So unless your going to do PC3200 (which is about the same price as PC800), you should go with PC800. If you get the "40ns" Samsung PC800, you can overclock further. If you exceed 133MHz FSB, I suggest you drop the memory multiplier.
<font color=blue>By now you're probably wishing you had ask more questions first!</font color=blue>