Hi, I bought a "Titan Goliath" Intel Core i7 930 2.80GHz @ 3.60GHz Quad Core DDR3 System from OCUK a couple of years ago, I'm looking to upgrade the RAM to 8GB+ (whatever I can afford really) The RAM thats already in is TR3X6G1600C9, is it possible to just add a 2gb stick or do I need to replace the lot?