You are gonna want a Quad core for video editing depending on your budget look into a Phenom II x4 955, I5 750, or an I7 920. The Phenom will be the least expensive and the I7 will be the most expensive.
If you can wait for sometime then the AMD THUBAN series 6 core processors are going to be out soon.. If all the news is to be trusted, you would soon be getting two extra cores of performance for the price of the current intel i7 930.. That's value..
amd hexacores will be making their debut on the 26th, so maybe you will want to wait for those, also if the apps you use support cuda, you can unlock the power of an nvidia gpu, food for thought, peace
What is your budget?
The most capable cpu out today is the Intel i7-980X with 6 cores @3.33 and hyperthreading, giving 12 threads. If your application is multi thread enabled, that is the best, excluding workstations. It will cost about $1100.
A top cpu would be the i7-930 @2.8 for <$300. ($199 @ microcenter). With 4 cores and hyperthreading(8 threads), it can do a lot of work. It can easily be overclocked to 3.3 and beyond. On a clock for clock basis, the nehalem cpu architecture is a bit faster than the AMD offerings.
On a value basis, lesser offerings give you a fair performance for the dollar. The choice will be based on other considerations.