Hi - I'd love some buying advice from folks who happen to be in the Retina iMac club. I'm planning to purchase an iMac from either the Apple refurb site or Other World Computing. I noticed that OWC/Macsales has some pretty good deals on nicely spec'd out Late 2014 5K iMacs and some 2015 models as well. However, I'm a little concerned that the 2014 model may not give that great of performance due to the 2GB GPU. Is it worth it to wait for a better deal on the refurb 2017s or purchase a refurb 2015 model instead? I'm going from a modest 2015 Retina 13" MBP and will be using the machine for some moderate graphics and photo editing work. Thank you!