Omnipotence = all powerful. I think this necessarily means that "capable enough" implies weakness, or the idea that something stronger exists, which cannot be. A question such as "Can God create a rock that He cannot lift" would be an illogical question because of the way it is framed. It would be like saying, "Can this mechanic, who can fix anything, fix this car that can never be fixed?"
I recall back during my college years wondering about a related problem concerning God: what if God as we know Him is merely the Master of our world/universe, but He is actually subservient to another, greater god whom we do not know? We might never know because we only know God. And we could continue that to say that this "greater" god could himself be subservient to yet another god who is still greater? And we could keep this going.
I think that many answers regarding the nature of God can be answered by considering the explanations discussed in Thomas Aquinas' "De Ente et Essentia" (On Being and Essence).