I'm looking for a gaming computer (nothing tooo hardcore) that will run all the latest games without lag. My budget is in the $700 to $900 range. Would an Alienware X51 base model run a game like Mass Effect 3? any recommendations will be appreciated
The best gaming computer is going to be the one you build for yourself. It's very gratifying knowing what you're running, and how it's all put together (not to mention the cash savings). There are several articles here on Tom's that show which components can be pieced together at certain price points, and all will fit what you need, as well as tutorials on how to actually get it all put together.
If you don't feel comfortable building your own rig, I would steer clear of Alienware. Sometimes you can find good deals when they have a clearance sale on older items, but most of the time you pay way more for the name and shiny lights than the system. I would suggest going to one of the other gaming rig websites, like CyberPower or iBuyPower. They offer a number of pre-configured rigs with varying levels of customization.