The 740m is better then the 7670m, without knowing what resoultion you would be playing at on this laptop (Im just going to assume 1333x768 resolution) you should be able to play at low settings at the very least but, at medium, my guess you will have some "choppy" play playing online.
At the price point you are looking at ($850) Ive seen much better laptop specs, one of the most popular cheap gaming laptops are the Lenovo Y510p or the Y410p, the cheapest variations of both start at either $719 or $799 and this does not include the coupons Ive seen being used online. Both of these laptop models have slightly different variations (some feature better resolution or a i7 processor) but anyone of them are better then the one you are looking at currently.
You should first go over look at the Lenovo website and check out which specfic variation fits your price and performance (for example the 410p is a 14inch laptop the 510p is a 15.6inch laptop or a i7 processor over the i5) and then see if you can find some sale or coupon that Lenovo seems to be having every other week