Advice on usefulness of MGMAT class for my situation

Well Ive been reading the board for a couple weeks as I prepare to take my GMAT and would love to hear anyone's opinion on my current situation. I am currently trying to decide if I should take the MGMAT course or just buy the MGMAT books along with the OG11 and other OG books suggested on the board and study on my own. A couple months ago I bought the Kaplan premier book, took the sample that was included in the book to see where I was at, and scored a 630 (39Q, 41V).
I felt like this was a good starting spot and spent the next 4 or 5 weeks going through the book. I then took one of the exams on the CD and scored a 560. I couldnt believe it (I hadnt yet discovered this site so I didnt know what a poor indicator the Kaplan CD exams can tend to be) that after studying my score could fall and fall by that much. I thought it had to be an off day so I took another tets on the CD and scored a 560 once again.
At this point I decided that self study was hopeless for me and decided I would take an MGMAT review course to get the help I needed. I took a week off from studying and began scouring the message boards at this site. From my reading I found that alot of people feel the Kaplan Premier CD tests are a pretty worthless (is this correct?) and I decided that I needed to take a GMATPrep exam to get an idea of where I stood.
Today I just took the GMATPrep test 1 and scored 700 (44Q, 41V). At this point I cant decide if I should just buy the books that are highly recommended here (OG 11, MGMAT SC book, etc) or up and take the classes. I have no self-motivation issues and believe I can push myself to work hard. My main areas of weakness are sentence correction (75%+ of my verbal misses) and some exponential manipulation and other algebra based issues. Am I correct in assuming that my time would be better spent studying on my own versus spending alot of time in a class where I am only looking for help in a couple specific areas? Sorry for the long post but I dont want to drop the money on the class if I can help it and I cannot make a solid decision without second guessing myself. Any help is appreciated.