Hi!
I completely understand your dilemma. Having never taken a GMAT class, I cannot give a complete and impartial review of both sides of the coin, so to speak.
For my prep, I used all of the
MGMAT series (not the intro stuff though) and OG13. Whenever I came across a question I could not solve, I took to these forums and found solutions that were both illuminating and easy to understand. When I felt I needed a greater challenge in Quant, I turned to the "700+" collection, which, if used correctly, will familiarize you with all of the ins-and-outs of the more complex aspects of the Q section. Follow the link to get to it:
700-800-level-quant-problem-collection-detailed-solutions-137388.htmlIf you're feeling shaky about the fundamentals, and feel that you are either a) a visual learner or b) learn better in group/classroom-type settings, I would recommend a course. If you're the type that needs ample time and solitude to really pore over the material, you may be better off doing the lone wolf thing.
I assure you that there are legions of people who have tried (and who swear by) each of the options. You can't go too far wrong, whichever way you pick.
If you feel you are strong at self-study, I would recommend you try going it alone for now, given that you have all of the books that you'll need. If, after a month or two, you feel like you haven't progressed, it might be time to sign up for a class.
I hope this helps! Don't hesitate to PM me if you need some more support.