Yep. Tea Urchin is right - the games are bottlenecking at the GPU and the rendering is bottlenecking at the CPU. Some of the Alienware products are nice and use good components, others are made and sold on the cheap. If you're looking at a CPU, GPU and RAM upgrade, it probably makes more sense to look for a replacement system. If you're comfortable to look on the used market, as many on here are (myself included), you could have a nice updated system for the same money that you sink into all the new components you'd need to upgrade, including a better power supply as mentioned.
You can get into a nice i7-3770k PC for as little as five hundred if you hunt around - track some auctions on eBay and scour ads on Craigslist in your area. I found a system with an i7-3930K, GFX 690, 1500 watt PSU, Rampage IV Extreme and 16GB of RAM for $650 and got to see it in action before purchase, so there are deals to be had if you look around. But at this point you're looking at replacing many of the major components in your machine at which time it usually makes sense to upgrade.
Let us know how it works out, whatever you decide to do.