I'm just going to straightup say that I really can't see anything, anywhere, that leads me to think pre-made computers have become anywhere as good bang-for-your-buck as building your own, except in really low-end rigs (and even then, not often). That doesn't even include the other benefits of self-built machines.
So yeah, just build it. Putting stuff together these days is super easy compared to when I was putting my first one together as a kid, and you know there's tons of people you can ask if you really get stuck on something anyway.
EDIT: Also, totally with Waff on Corsair cases. They are extremely good pieces of tech. I personally use a Thermaltake Level 10 GT, but that's because I wanted a water-cooling friendly case, I adore the look of it, and I just felt like it.
So yeah, just build it. Putting stuff together these days is super easy compared to when I was putting my first one together as a kid, and you know there's tons of people you can ask if you really get stuck on something anyway.
EDIT: Also, totally with Waff on Corsair cases. They are extremely good pieces of tech. I personally use a Thermaltake Level 10 GT, but that's because I wanted a water-cooling friendly case, I adore the look of it, and I just felt like it.
[SIGPIC][/SIGPIC]
This lil' thing is thanks to Jarka!