"Enough" depends on who is taking the test. I'm convinced that my good score had more to do with taking practice tests than studying the material. I took 8 practice tests: AAMC 3r, 4r, 5r, 6, EK 1g, and 3 TPR tests.
Another note: None of the non-AAMC tests come close to the quality of the AAMC tests (go to e-mcat.com). They're of much better quality; all of the answers make complete sense, which is much more than you can say about the EK and TPR tests.