I just ordered my iMac from Amazon. Looking up RAM prices and found 4gb RAM modules for 49.99 each. Was thinking about buying two to stick into my new iMac since it supports up to 16 gb of RAM. What configuration should it be? 2X2X4X4? or 2X4X2X4? And is it worth it? Will the extra 8gb of RAM make a huge speed difference or is it pretty much like sticking jet fuel in a Toyota Yaris? It'll work but just kind of a waste of time money and effort? Would just getting 2X2gb modules be better? I can get one of those 2 packs for 50 bucks total. Thanks in advance.