Well there are several things wrong with what people told you.
First, you cant add a GPU to laptops except in some special cases, and even then, you cant add desktop cards.
The 290x is a very powerful card that will last years, all cards will under perform eventually. The 860 hasnt been released let alone the specs, and it will likely fall at the same times the 290x does.
EDIT: 860m is much different than an 860 and I realize that