The specs you posted makes that rig sound like a beast compared to what a lot of other people are using to play this game.
That said - I would encourage you to try to avoid setting expectations the machine will not meet. Being disappointed with an expensive purchase is never fun.
For what it's worth, I purchased a new gaming laptop about 6 months ago, and have had mixed results, at least where TS3 is concerned. My rig has 12G of i7 RAM, a GTX670M 3G video card, and SSD. It is true that the graphics on high settings are really gorgeous. It is also true that the game lags, freezes, and sometimes crashes, even on this machine.
The Sim routing (pathing) engine is quite a complex animal, and sometimes Sims get stuck. Over time, more and more Sims get stuck, and I believe that is one of the causes of game lag that develops in a game you've been playing over several Sim weeks. If you're not using Twallan's Overwatch, I have found that an occasional resetsim * is also very effective in resolving lag from that particular source. A more powerful machine can run software more smoothly, but it can't fix problems that are inherent in the software itself.
Best of luck with the choices before you, and happy Simming!