Let's just skip some steps, alright? There are some simple rules for buying a satisfactory computer. You already have figured out two important ones:
- How much are you willing to spend
- What are you going to do with it
If I have understood you correctly, you'd want to do some surfing and office routines. Plus you'd like to play AH with a decent frame rate. For the first two almost
any computer built during the last decade will do. AH is the toughest of those three.
Almost every program has a list of minimum and recommended requirements published somewhere. When you're choosing a computer, look for the most demanding program you're going to use, look at the recommended requirements and add some headroom for the most craving components (CPU, RAM, GPU). In this case the recommendations are
Windows 7
2Ghz Intel Core 2, or faster
System RAM/Memory 4GB
Video Card DirectX 9 compatible with 512MB of RAM
Take these and double the amounts for a decent rig for several years. Gyrene81 up there has some suggestions of today's hardware, he's more up-to-date with it than I am.
Fancy power cord thingie... It seems like you've been looking at the pictures of some rigs on this very forum!
Now there's two kinds of power supplies: Regular and modular. The thing with modular ones is that you only plug in the cords you need. Unfortunately, at least AFAIK, there's often more than enough permanent cables and plugs even on a modular PSU!!!
Anyway, the idea is good. A hamfistful of cable spaghetti in the middle of your case will certainly hinder airflow. That's the whole idea of cable management, to make the inside of a case as open as possible. Extra fans serve the same cooling purpose, plus they can make your computer quieter. You see, one whirlwind makes a lot more noise than a bunch of cool breezes. The amount of airflow would be similar, but the whining and grinding only a fraction. Strategically placed fans can also aim the airflow to a desired point where the cooling is most needed.