i would add one thing to your list... power supply.
when i talk to customers who are shopping for a desktop, one of the first things i try to do is to get to know what the needs are. if the person 'games' on the desktop, there's a good chance they may want to upgrade the video card sometime down the road.
i try my best to make sure the customer understands that video cards have power requirements. many of the lower to mid range desktop systems do not have a psu (power supply unit) that can support higher end gpu cards. i inform them that if they do intend to upgrade their graphic cards in the months or years ahead, they should be prepared to purchase a more powerful power supply. if they don't want to deal with that, then there are also higher end desktops with more powerful power supplies. for example, the current gateway fx has a 750w psu (if memory serves me correctly), compared to the 300w-ish psus you find in most mid range desktops.
