CPU will make little difference but you get a slightly better version if you take the higher spec one to upgrade with gpu and ssd upgrades. RAM is set at 16gb currently for numerous reasons but that is the only option available (mainly balancing battery drain) the 460 gpu upgrade is a no brainer its fairly cheap for an upgrade and is a big improvement graphics wise (460 is the best card they use in the MacBook pro with a rated 1.8Tflops its about as powerful as a playstation 4). All you really need to do is decide if 1TB of storage is enough for you or are you willing to shell out for the 2TB upgrade.