Quant questions in
MGMAT CAT are more difficult than those in GMATPrep. I personally think that if you get Q43 in
MGMAT CAT, you may get 45-46 or even 47 in GMATPrep. My quant scores in
MGMAT CAT were 41-44, but I got 47 or 48 in GMATPrep and scored 47 in the real thing. So, don't worry about quant score :D.
I suggest reviewing quant problems in
MGMAT CAT to learn new concepts and spending time on CR and RC as well. Though you might be quite good at SC, do not forget to practice this section; a set of 20-30 questions per day is enough.
I myself find that revising the incorrect and correct answers I got in GMATPrep is critical. I googled the incorrect ones and read carefully (and even took notes) the detailed explanations of Ron and Stacey on
MGMAT forum. It really helped building my concepts in quant and improved my knowledge in SC.
650+ should be attainable. Goodluck!