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Nahh, you can buy a CPU that's 80% as good for 20% the price.
Make it quad core dual processor, add tons of ram (which is just regular DDR) and you can build a mac that is just as fast as a Mac Pro for around $1000.

Not to mention, you could go the new Core i7 route which every benchmark I've seen out performs the Mac Pro's XEON processors.
 
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