Hi, I have the first generation mid 2012 15' rMBP 16GB/750GB which seems a little bit slow now. I'm looking to upgrade to the latest force touch capable rMBP. The SSD is definitely going to be faster and I can drive 4K external monitor which I currently only partially can. But is there going to be a huge performance difference in terms of CPU/GPU? Or should I wait for the next gen? I'm planning to do a clean OS install first to see if there's an improvement.