Still debating replacing my 2009 2.93 dual core iMac with 4GB memory with a late 2015 3.2GHz QC i5 with 8gb (likely upgrade to 16gb) and was curious as to the % performance increase I'll see. My current iMac is really dogging now. It's either the newer iMac or a new MacBook Pro - but bang for the buck and more conventional inputs has me on the fence with keeping to iMac. Are we looking at a machine that's 2x, 4x, 10x faster than what I have now? Anyone know?