I've seen grumblings that AE CS4 is slower than CS3. My Adobe 'Creative Suite' is older than any of those :lol:
The problem with the 'money no object' crowd, debates on forums like this and the Creative Suite package (using i7 as an example - not slamming on it) is Adobe for the most part is more dependent upon setup, RAMs and fast disk I/O.
A fast dual core (let's use the e8400 in this case) properly configured will kick a quad's arse in most of your standard tasks. I think this is where your friend's problems are with his *lag*.
It would help to know more about his current hardware setup. How are his hard drives set up? What type of hard drives? How much RAMs does he have? Does he use a 64-bit OS?
IIRC the 'sweet spot' with a Windows OS is to assign 55% or so of system RAMs to Adobe - this leaves enough memory left over for the OS, background services and other open apps.
With AE CS4 you can set the amount of RAM that each core utilizes. For this example let's say he has 8Gb total and assigns 4Gb-5Gb to Adobe. With an e8400 (or maybe even a Phenom II 720) the amount of RAMs assigned to each core would be greater than that assigned to each core of a quad .... meaning you are less likely to be slowed down by hitting the paging file (which is most likely where his 'lagging' is coming from - that, and his disk I/O).
Now ... where the i7 will help your friend (at least
today) is in the final encode (this is also a whole 'nother debate because of *AE Render* and the current & future possibilities of using the GPU for parallel processing).
CS4 has introduced GPU processing which 'blows away' CPU processing by 500%+ in some Adobe tasks - it will be quite interesting to see how this new tech evolves in the next 12 months ...
AE Render is CS4 distributed computing ....
You can use the aerender application to perform rendering operations on multiple computers as part of a render farm, or you can use the aerender application on a single computer as part of a batch operation.
Lookee here ---->>
http://help.adobe.com/en_US/AfterEffects/9.0/WS8A8CD670-4A72-4fb5-AE8E-CB9E232EC0B5a.html
So .... this is where you have to be careful with your 'friend' and 'money is no object'. If you drop $2-$3k of his money on a rig which gets its arse kicked in 12 months by a $500 rig he may not be your friend anymore.
My advice is to invest in fast hard drives (Raptors to start - SSDs as the tech improves and prices come down), get him on a 64-bit OS with a minimum 6-8Gb of RAMs and 'go low' with either an e8400 or Phenom II 720 mobo/cpu combo. If this is 'serious business' for him you need to help him plan a render farm and central storage (with 'lower priced' dual core CPUs) with an eye toward putting a GPU in each of those nodes as the tech advances.