I know I'm late to the game on this, but honestly? Use every resource you can get your hands on, especially if it's free!
When I was prepping, I didn't think Kaplan was complete enough to drop $2k+ on a course (nor did I have $2k+ to spend. If I had decided to pay that much for a course, I wouldn't have been able to afford any other prep materials at all, and would have missed out on AAMC's Section Banks and a couple of practice exams I bought from elsewhere.
Do keep an eye on the Official Guide MCAT outline... If there's anything you don't get from your course, or feel you don't completely understand, or they are dead-set on an approach to a subject that doesn't work for you, supplement! Good supplements include books from other companies and of course Khan Academy. And hopefully not having to pay for the course itself frees up some funds so you can afford those supplementary materials, or for AAMC practice materials.