Have read a few posts on various forums about the failure rate of the dedicated Nvidia 650M thats in the 15inch MacBook Pro from mid-2012. Did this iGPU come in ALL the 15 inch models? Or do some of the lower end configurations have only the HD 4000? Also, is this more of a "when" it will fail vs an "if"? There are a few nice machines near me for sale on craigslist in the $400 range and was thinking about upgrading from my late-2011 13" i5. However, I will be using it with an external monitor from time to time, and have read that the 650M powers the external display when connected. Should the 15 inch models from 2011 - 2013 be avoided altogether due to the faulty dGPUs in these machines?