I know what you mean. I did shopping also and didn't know what to get.
Last weekend I built a system with a e6600. I notice that all your choices are OCZ. that's what I bought and one was bad. Had to send the pair back OCZ support was good and quick, but it cost ME to ship it back and with the holidays it could be a couple of weeks to get it back.
At any rate, my uninformed opinion is to go with the 800.
I was thinking about going with some DDR2 533, but then I found out that my motherboard would overclock fairly well with some good ram. And theres really no point in getting something that is "slower" when you can get something that is "faster" for 10 dollars more.