I had but had to return the base configuration Retina iMac because of dead pixels. I'm about to re-order, but am tempted to get the upgraded CPU & GPU. I am, however, concerned about all the complaints I've read, here and elsewhere, about heat and noise issues with the upgraded machines. Mind, during the short time I had my base machine, I notice nothing amiss regarding these issues, but I'm a bit wary of ordering the upgraded GPU/CPU and regretting it (due to heat and noise). Any words of wisdom/caution? Thanks in advance.