Don't buy a shitty alienware.
I was in the same situation as you.
I was deciding between the Samsung 7 Series Chronos NP700z7c or Lenovo Ideapad y510p.
I went with the Samsung and I absoutly love it.
Check the specs here.
I love my Samsung, but if you want better graphic power go for the lenovo y510p with SLI 4GB 755M.