(Wandering topic)

I wouldn't bother with an older Mac Pro unless you *NEED* the expansion slots.

The just-released Haswell processors are so fast that you'd need a 12-core Mac Pro to be faster. If the Mac Mini moves to desktop processors (which is should/could with Haswell,) an updated Mac Mini will likely be faster at everything but gaming than an 8-core Mac Pro. And it should be faster even for gaming than the stock video card that shipped with a 2009 or earlier Mac Pro.