I would like to buy 512MB of extra RAM for a new 12" PB I am about to order. I would order the RAM with a BOT through the apple website, but it is very expensive that way. What manufacturer do you all suggest for the RAM, or is it essentially a commodity item and one is as good as another? I have online prices of $130 for GVP, $150 for Edge, and $160 for Kingston. Also, is it easy to install yourself? Would I invalidate the warranty if I opened up the computer to install it? Thanks in advance.