The benefit of using more material, online or paper, is that you'll be more exposed to material. The downside to using another philsophy-based course (that is one-size-fits-all) is that you might find solutions to the questions that run counter to the way you've just trained - - if you get enough contridictions, I think that you run the risk of your efforts potentially backfiring.
An effective strategy would be to focus on the official guides, paper tests, hard questions (like kaplan 800 without using their explanations) and frankly, getting yourself a detailed evaluation of where you are NOW, to see why your timing isn't up to snuff: do you need to get back to the basics of the material itself (ie. grammar, math, etc.)? Or do you need to find shortcuts, strategy, ways of thinking, and hone your ability to respond to the 'GMAT writers' voice.' I think to launch into the basics all over again via a big-company approach might be annoying, boring and redundant, and ultimately, busy work. really the most important thing is to make sure that whatever you do is not contradictory to what you've done up to now.
Hone your skills, and if you can, consider working with a private tutor/specialist on the areas you need to improve. It's more efficient and would in all lilkihood have a greater ROI at this stage of the game.
Good Luck!
