I would go for the i7, considering what you need this system for.
HDD- Whatever I can get cheap and is fast.
320GB or so is about the minimum you can buy if you want it to have decent performance.
Newegg.com - SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
$55, one of the fastest consumer drives on the market. If you have the money, you could get a small SSD for the OS and programs, but if you're after cheap
and fast they fail there :P They are insanely fast, though.
The OCZ is a bit of overkill, you could get away with 550W easily. As long as it has 500W and 2xPCI-E 6-pins, you'll meet the requirements.
The HD5850 could be overkill, but I'm not too knowledgeable about the application of ATi GPU power in CGI and photo/video editing.
Out of curiosity, why the network card? For the average power user the one(s) in the motherboard usually suffice.
Otherwise, everything is good.