xt??how

I own a DV6 6121tx and the only bottleneck I found was its HDD. I also contemplated buying a new Envy 15 ( Yeah,I'm a HP FanBoy,and HP's have served me awesomely till date),but it also came with a 5400 rpm drive. So,with Budget fixed at around 12k(Max),I have the following questions in mind...