It should be fine, although I would swap the gfx card for a 4850 or a 4870. Also the E7300 is good but if your tight on money get the E5200 since it'll do almost as well as the E7300 but at a much lower cost. With the money you save you might as well pick up the cheapest P35 mobo you can find, but I'm more of an Asus person so... Get an Asus mobo...
Also, 2 gb of ram is a little too low, at least for my taste given with today's drop in memory prices, you might as well get urself a 2x2gb sticks unless you're using Windows XP 32-bit, then just stick with the 2gb as they'll do just fine.
Is there any reason you're scared to build? If you can read a manual and feel comfortable upgrading computer components, you can build your own rig. Pre-built computers always cut corners to save $, especially with the power supply. The power supply is the heart of your system and should always be good quality or you risk it taking out your whole system. The system linked to is a decent computer, but you could build a better one for not much more $. Something like this would be awesome:
The other question is , is the Warhead PC going to be locked down in anyway shape or form, IE proprietry BIOS, locked features onboard. As this can cause issues with upgrading later on.