My advice would be to stick with the official GMAT content. There is a long list of reasons why that is the best choice but you have to take my word for it. Use the following content if you have not already:
1) Two free GMATPrep practice tests.
2) Two additional CATs that are part of Exam Pack 1.
3) GMATPrep Question Pack 1 database of questions.
The official GMAT questions have the same style and format as the real exam and it is best to get yourself in the mode of handling those questions.
Also, you will gain more by pushing your verbal score. Of course make sure you maintain your quant or perhaps push it to Q50/Q51.
Cheers,
Dabral