If you want to play Skyrim at Ultra, you should aim at GT770M/GT755M (SLI)
You can see what framerates you can expect here (No. 39 & 42)http://www.notebookcheck.net/The-Elder-Scrolls-V-Skyrim-Benchmarks.66057.0.html
The Lenovo Y510p is the best budget laptop having GT755M (SLI). (Check out the 5th model)http://shop.lenovo.com/us/en/laptops/ideapad/y-series/y510p/#customize
GT770M models are above 1500$, if you're interested.