As I understand it, many of the later model MP's are basically similar machines. Generally speaking, can anyone offer any insight on the price/performance ratios of these machines on the used market? Does one model suggest itself more than others? I'm upgrading my MP1,1, which has an SSD and a Radeon 4870. I understand that my SDD should be even faster in a newer machine, and I can drop in pretty much any GPU, right? Should I consider certain models to make my GPU selection wider? I would *love* to get the R2D2, but the more I read the less fascinated I am. Sure, Thunderbolt would be great and the SSD would likely scream, but the GPU offerings are a joke (the best model is the Fire version of the 7970, which isn't even sold any more) and will cost way too much. Am I missing anything? Can anyone offer a reason to get the new model that I might be missing?