6 gb is enough for most tasks. I've seen some used for $50 on craigslist, but offer $40 instead or check newegg for rebate specials. 1333 ram is more than adequate; some boards default to 1066 speed anyway, but you can usually set it manually in the bios for 1333. And do go with 3 or 6 stick kits. If your board is non oem (not dell, hp, etc), then check for a ram qvl listing on the board webpage. It will give you some brands that are tested; you don't necessarily have to match the model number exactly. I recommend standard CL9 ram which runs at 9-9-9-24. Kingston, crucial, corsair, gskill, and patriot are all pretty good and offer lifetime warranties. Also stick with 1.5v rated ram, which is recommended by Intel.