For the lag issue you should invest in Killer Nics. (http://www.bigfootnetworks.com/)
For higher FPS, I would suggest getting an SSD since most hard drives are the most common bottlenecks on computer systems in general.
The new egg link doesn't work.
As for alienware computers, remember that you pay up front and have to wait a few weeks to receive the computer. I don't know if you can get a decent gaming computer with those two devices under 950 though.
Wrong on both accounts. The Killer NICs have been proven to provide a very minimal gain in terms of latency AND FPS unless you're normally doing things while playing games that can kill your latency (such as downloading via torrents). And even then, you can use third-party free software that will give similar results. SSDs while much faster than conventional hard drives will not speed up your FPS in a game. They may decrease your load and save times a bit, but not much more than that at all. The three most important things to your FPS in a game are your CPU, your GPU, and RAM.
3GB or more of RAM is more than sufficient for any game currently out although more would be recommended for future titles and/or if you plan to multi-task a lot. As for GPUs, there are a ton of options out there making it hard to choose the perfect one for you. Ideally you want to find one around the 200$ price range as they tend to offer the best price to performance ratio.
I wouldn't recommend getting an Alienware, ever. They are essentially nothing more than a different looking Dell XPS so you end up paying a lot more for looks and a name. I'd highly suggest building a custom PC yourself or finding a site that builds custom PCs at a fair price. You'll get the most for your money that way.