The imac is not a processor. The imac is an OEM manufacturer that builds computers with processors in them. The imac comes with an Intel core i3 dual core 3.06GHz processor.
Is it a good choice? it will work.
Is it worth the cost? no
The best processor for video editing is of course the most powerful processor available in consumer desktops: The intel core i7 980X, which costs $1000.
Is it a good choice? better than any other processor.
Is it worth the cost? The performance you get out of it for $1000 is not worth it.
So what processor should you get? Well that depends on many factors, such as:
- How much money do you have to spend on just the processor?
- How much performance do you need? For example, are you in a business where you have to complete these within a certain timeframe? If the timeframe is very short, you might even want to look into a dual or quad server setup. up to 4 processors in a single system.
That said, I recommend a few guidelines. You'll want to look at a quad core at least, as most programs you have mentioned and most programs in your field can make use of multi-core setups. You'll want to look between the Athlon IIx4 3GHz at $100 and the i7 980X at $1000. Most processors over $300 are getting less and less performance improvement per cost as you move up.
So good bets are the entry level core i7s and the Phenom II x6s between about $200-300.
On the front of between $150 and $200 the i5 quad core and Phenom II quad core are excellent processors but lack efficient threading past 4 threads at once.
If you are interested in the mac road, it is trodden with overpriced hardware and compatibility issues with most windows program however, now mac has finally allowed windows to be installed on their computers in a dual boot mode. Although this kind of defeats one of the main purposes that most people buy a mac: the like the mac OS. That said, you would have to look up all the programs you use to see if they have versions for mac.
To keep in line with my previous suggestions, I recommend the 27" mac to get the quad core at least.
Now, this isn't to say the lower end mac or a lower end processor won't work well, it will work fine. The other processors I have mentioned are just very fast. Note that the Athlon IIx4 at 3.0GHz is one of the best price/performance CPUs on the market, especially for heavily threaded applications such as yours.