CPU: go quadcore or i7 - good for encoding speeds.
RAM: i'd say about 3GB of DDR3 RAM for 32 bit OS (only recognises 3GB even if you put more in). Bump it up more if you willing to go 64bit OS.
HDDs: get 4 x 1.0 or 1.5 TB. Get as big a cache as possible. Go for a 10,000RPM speed if you can put up with the noise. Make sure they are all the same size, and same make if you want to use RAID properly. Use a seperate HDD for the windows install partition - get a small SSD for maximal boot time/responsiveness. Hell, if you really have no budget - get all SSD drives. Be warned this will be ******* expensive, and probably wont be 4-5TB.
need a decent GFX card for encoding/playback. I'm not up to speed on current ones - sorry.
MOBO: depends on CPU type and RAM type really. Most midrange and above have RAID these days. MAke sure its DDR3 even if you dont get DDR3 ram (futureproof for a good few years).
Since you say no real budget - I would say, are you willing to spend like 5grand on this? If so, you can go for overclockable CPU/MOBO/RAM combo, watercool it and OC the *** out of it.
Lol.
Have a feeling you will find a budget limit somewhere - so do some homework on prices and decide how much you're willing to spend.
Nathan