Portable desktop for gaming

I´ve been looking into laptops for the last 3 months or so, but to get a decent gaming laptop I´m looking at spending at the very least $1,000 and they are not really upgradable. So I´m wondering if there´s really any good options for a gaming dekstop that gives me more ¨bang for my buck¨ but still being somewhat portable. I´m looking to play mainly RTS´s and RPG´s. Especially the Total War series (including the new Rome Total War 2.)

Any advice is greatly appreciated.

EDIT:

I´m open to building myself as well.