Well you stated 3 years and thats a long long time for a laptop, laptops generally dont last that long. System specs you provided are OK! esspecialy at 720p its very do-able. you can go ahead and get the laptop but if possible an SLI laptop would be ideal. If you are willing to set games to low or medium after 3 years then surely go ahead.
Just dont forget to buy a laptop cooler if you will be gaming intensely on LAN party's, its an absolute must, a laptop cooler will also increase your performance and stabilize FPS because laptops clock themselves down once they reach about 90 deggree's which can happen and happens very very often to laptops.
765m = a 650 TI
770m = GTX 660
performance laptop compared to desktop!.
Check this link:
http://www.notebookcheck.net/Mobile-Graphics-Cards-Benchmark-List.844.0.html
If you can get a 770m for around same price its worth it as far as im concerned but it depends on what you personally want and/or can.