I'd say you make your own because it's always fun (and I hate giving money to Alienware... makes me feel like I'm a N00B for some reason =P). But why not get the Athlon FX on your self-built computer? You really don't need 400gb of space unless you absolutely need it (which it doesn't seem like it because of your HD choice on the Alienware computer). Get like a 160gb SATA hard drive and invest a little more on the CPU/motherboard combo. You might be able to save a little bit more money on RAM if you choose not to overclock.