It depends to a certain extent on what size laptop you want; a 17 inch will be a mobile powerhouse but at the same time could probably compete with a college bio textbook for weight. At the same time a 13 inch will probably be light but could have less than admirable hardware or could have heating issues due to the fact it's tiny.
But regardless, check out the 14" lenovo y410p. It's got good hardware and price starts at $780 (more for more upgraded models of course)
core i7 4700mq
8 gb ram
gpu is (i believe): GT 755M
1 tb 5400 rpm hdd
^I'd recommend the option that included the 24 gb ssd drive if you can afford it, I definitely enjoy the speed increases
The case is a bit flimsy in places, but if you treat it right then it should...