Well yes, a more complex gear box *is* capable of different things than a less complex gear box. If you have only two gears, for instance, you certainly can't build a calculator out of them - but Charles Babbage was able to make a calculator out of hundreds of gears!
(Well, OK, I suppose you *could* build a calculator out of two gears... but the "calculator" would only be capable of very simple calculations like multiplying numbers by the ratio of the numbers of teeth on the gears...
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And while the human brain is not made of gears, the components (neurons) that it IS made out of are not much more functionally complex, and can easily be emulated. I know that neurons have internal components such as a nucleus and cytoplasm, but in my opinion at least those are just "implementation details" - a neuron would be a neuron whether it's made of cytoplasm or crystals or whatever. I think it would be arrogant and shortsighted to assume that creatures worthy of moral consideration could only be composed of organic components. Even if God made man in his own image, could God not have created creatures that were not in his own image, but were still self-aware? And with intelligence and free will, whether they come from God or not, could not man create creatures of his own that are self-aware? We already do, of course; it's called reproduction; clearly *something* is being transmitted from parents to children that gives them the capability of self-awareness; it might be genes, or it might be the essence of God, or it might be the Force, or it might be farandolae (those fictitious mitochondrial parasites posited by Madeleine L'Engle in her novels that supposedly grand humans special powers), or maybe a combination of factors, or maybe something we don't even know about yet, but whatever it is, I'm confident in humanity's ability to duplicate it artificially at some point in the future.
Maybe it's just a philosophical difference between us - I tend to believe in things that I can perceive, and consider abstractions to be "less real", so if I perceive a computer to be acting in a self-aware manner, I'd consider it to be self-aware. Since I can't seem to perceive God (apparently something is lacking in me because everyone else can!), I don't consider God to be as "real" as human beings or computers or chairs or planets or whatever. Maybe that's what draws me toward the Buddhist/Jewish philosophy of focusing on improving the here and now, and drives me away from the Christian/Muslim philosophy of treating the here and now as irrelevant compared to what comes after... the strange thing is, both philosophies seem to practice the opposite of what they preach - Buddhists seem to not be much into worldly activism, while Christians go nuts about it! Perhaps things will change though as cultures blend... I've read reports of Tibetan monks being involved in protests, and yet there are a lot more interfaith dialogues than there used to be...