Gigaram

Hey, I'm definitely upgrading RAM in the very near future, and I need a little help. I'm willing to spend about 90$. I've got some questions however.

Say I have PC3200 RAM now, and I buy PC3500. I'm under the impression that the higher speed RAM will underclock itself to match the lower speed? If this is true, is this underclocking permanent, or would I be able to buy more PC3500 RAM later, and switch that with my current 512 PC3200?

Not only this, but I'm looking at Gigaram on newegg. Any reviews with Gigaram? Also, what would you recommend, PC3500 or PC3200?

http://www.newegg.com/app/ViewProductDesc.asp?description=20-221-005&depa=1

if you use a stick of pc3500 and run it with 3200 then it will run at 320o. If you remove the 3200 and run it with 3500, then both stick will run at 3500. http://www.newegg.com/app/viewProductDesc.asp?description=20-156-008&depa=1 , <-- that is cheaper and at pc3500 speeds than the ram you posted, and kingmax isn't that bad