Umm, tough question. Because there is so little info it's really hard to say (in fact I would not have commented, but your livelyhood is at stake) what you need. Can you give us the specs on the system you are currently using?
Next, I need you to fill out this form: http://www.tomshardware.com/forum/274745-31-step-step-guide-building
It may seem redundant, but there is important info we need.
I can tell you right now that if you want to get serious with editing you should probably bump your budget to $1000. But we shall see.