Here's the CPU comparison Click Here and Click Here for a review of the Lenovo. And the datasheet Click Here says that it will take 16Gb RAM so you can upgrade it. Try a Google search for that model with the specs you need and see if you can get a price. If not you can always buy 2 8Gb sticks of RAM and sell the old 2 x 4Gb sticks.
Samsung Galaxy A9 review: Hands-on