A system clean up will not help much. His system is strong enough to run 50+ background processes without a sweat.
That depends entirely on what processes they are, don't you think? Some of the default installed things are really resource hogs. Even goin from a "mere" 40 processes down to 28 can make loads of noticable change on a fast system.
His bottleneck is most likely the CPU. AH can utillize dual cores best, and thus the more GHz, the merrier.
This means a 2,4 GHz quad is not an ideal processor for AH - and a cleanup will not change this.
Sure, it will not hurt either, but the results will be very minor, if noticeable at all.
Wrong. He is not bottlenecked by his CPU. His CPU is more than fast enough to run everything he throws at it. It's not the CPUs fault if the software is being slowed down. Don't forget you're not just sending raw data to the CPU. You're sending commands to an OS, and if that OS is bogged down and trying to compute stuff it doesn't need, it's inefficient in how it sends individual bits of data to the CPU.
Would you rather run a dust buster with a clean air filter or a dirty one? Clean air filter sucks things up nice and fast, but a dirty filter takes almost all the suction out of it.
In this case, running 50 processes is a severely gunked up filter, and no matter what horsepower you got behind it, the filter (the OS, the processes running) is going to slow down what goes in and what comes out.
P.S. You do realize that the core2duos redid the basic performance and efficiency of Intel processors, right? For any given GhZ rating, even a Core2Duo running on a single core will outstrip a P4 of the same GHz.
A P4 3.0 GHz can be outperformed by a C2D E6400 running at 2.13GhZ, probably. And that's a low-level C2D chip compared to a high level P4. They only get (much) better as you go up the ranks. His 6600 quad may "only" run at 2.4 GHz, but it's way better than a P4 3.2 GHz overall.