To buy and configure a Mac Pro, see my step-by-step guide.
Recently, Apple quietly added a 3.33GHz option for the quad-core Mac Pro, a custom configuration option at the Apple Store. I recommend buying refurbished if you can (here’s why), but this new model won’t show up refurbished for a few weeks. You can also save a ton of money on memory and drives, and how to do so is covered in my buying guide.
For most applications including Photoshop and Lightroom, the new 3.33GHz Mac Pro is the fastest Mac you can buy today— faster even than the 8-core 2.93GHz model (for most applications). Configure it as I explain, or contact me for a personalized consultation.
I’ll say that again: for most purposes, the quad-core 3.33GHz model is the fastest Mac you can buy! The only exception is for well-written programs that can actually make full use of an 8-core Mac Pro; such programs are few and far between and the list does not include Photoshop or Lightroom (for most common operations). But it does include programs like Genuine Fractals. See my Optimizing Photoshop study and Optimizing Lightroom studies, as well as When More Is Less.
Assuming ample memory and a fast RAID to eliminate disk bottlenecks, speed is directly the ratio of processor clock speed, which makes the 3.33GHz model 25% faster than the 2.66Ghz model, and 13% faster than the 2.93GHz model. As a $1200 upcharge, it doesn’t come cheaply, but it’s still less expensive than an 8-core 2.66GHz machine, and will provide 25% higher performance for everything, all the time, regardless of how many CPU cores are in use, as compared to a 2.66GHz model.
Oddly, there is no 3.33GHz option for the 8-core model (dual CPU). With Intel’s new 6-core processor looming in early 2010, it’s possible that Apple will stick to a quad-core model at faster speeds, forcing users that want the new 6-core CPU to buy a 12-core machine (dual cpu). Then again, that might not be the case.
The main limit of a quad-core Mac Pro is four memory slots (instead of 8), limiting memory to 16GB, which is not a real limit for 99% of the users out there. Also, users regularly running programs like Genuine Fractals, Helicon Focus, etc might obtain more benefit overall from an 8-core machine than a quad-core 3.33GHz (see my benchmarks). But most users will find the 3.33GHz option the very best one when maximum performance is the goal, because 3.33GHz is 25% faster than 2.66GHz; an 8-core 2.66GHz machine has to “win back” 25% by using more cores, and that just won’t happen with most programs.