On one hand I think that 4 core processor could have 4 processes at the
time, which in my opinion is better than 2 core cpu, but on the other one,
maybe AE could be faster with 3.33Ghz instead of 2.66 Quad core?
Well, on a simplistic level Navarro is of course right, but it all boils down to which OS you are using. If you merely use Vista 32bit or XP Professional 32bit, a dualcore is all you are ever going to need since you can't have more than 4GB of overall RAM in any case. Only a 64bit OS will play out all the advantages of a quadcore, in your case with at least 8GB of RAM. It also hinges a lot on what your typical workflow is - you don't need a quadcore if you are doing more straight editing than effects. All that power really only has a meaning if you are throwing tons and tons of effects on your footage and the average processing time per a given number of frames can be lowered by having 4 of them being calculated at the same time using multiprocessing, which may not always be possible. If you are working e.g. a lot with time-remapping and speed ramps, MP will not be used at all for these things.