Posted 25 May 2009 - 05:28 PM
Welcome to bleepingcomputer!
The system looks great and here are the answers to your questions:
You shouldn't need any extra case fans.
If you don't plan on using two or more graphics cards, you could go with a lower wattage power supply that's cheaper, but don't skimp on quality. That power supply is still a quality one, and it's not going to hurt anything if you do go with it.
The default heatsinkfan should be fine.
The motherboard looks great and Gigabyte is one of the top brands for motherboards.
The onboard network controller is fine, I wouldn't waste money on an upgrade because you probably wouldn't notice a difference.
The wireless cards are if you want to use wireless internet. If you get your internet through an ethernet cable, then you don't need one. You could always add one in the future if you do eventually need wireless internet.
You could probably save 100$+ if you built it yourself, plus you would have more options to choose from. We could help you with this too.
"I think there is a world market for maybe five computers." - Thomas Watson, Chairman of IBM, 1943