I really think that the AAMC tests are the best. I imagine that test V when it becomes available will be a good one that you should save for last. I thought that the actual MCAT was not significantly more difficult and my scores were similar to those that I got on those tests (my highest was a 12 on any given section, my lowest a 9, I got a 30Q)
Like I said, the AAMC are really great. Do you really need to take more than 5 practice tests?