Take the 3gb option @ 333 mhz for now.
Better yet, go to the web site of a good ram vendor, and access their configurator. Kingston, Corsair, OCZ, Patriot, and some others have them. Enter your motherboard, and get a list of their compatible parts. Their list is more current than the motherboard QVL lists, which aren't changed after launch.
Look for a low cost 4gb kit. As a heavy multitasker you will notice the difference.