I was just offered a Alienware M11X R1 for 400$ should I take the deal or leave it?

I would just leave it. The hardware in it is severely outdated for you to even give a look at it. I'll struggle to play games given it has the GT 335M graphics card. That's low-tier. Unless you want to spend your time playing Gmod in relatively low settings then I would avoid it. Save up more and get a decent sub $1K gaming laptop if that's your deal. Or build a desktop if you got the room in your home for it.

Look at laptops such at this: http://www.amazon.com/...00F0RC5O2/

Roughly $250 more and you can play games at 1080p at decent settings. I know I pretty much maxed Arkham City and Borderlands 2/Pre-Sequel with its GT 750M (just hitting the mid-tier) and newer CPU (i5).