I think that all low end PowerMacs should have one processor, so that Apple can satisfy the extra features that would make the PowerMac faster (DDR-RAM) and upgradable, while maintaining a low cost and basic features (CD-RW). It just makes sense.
It would not make sense for Apple to have all dual processor models. Otherwise, even the low end would be rather expensive, I'm guessing, $2400, to carry the extra processor. And Apple has recently been basing their PowerMacs with ~$1600, ~$2400, ~$3000-$3400.
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