First, we would like to say thank you for choosing us to help you beat the GMAT! We're very excited to have you!
As far as additional quant study materials, math essentials should be fine. Complete the booklet and then take the quiz that's in the math essentials book. If you are still feeling a little uneasy about your math skills Cliff Smith, one of our Guru instructors, recommends the book below from Amazon.comhttp://www.amazon.com/Short-Cut-Math-Ge ... 210&sr=8-1
Hope this helps and please do not hesitate to reach out to us, we are here to help!