Based on the reasons you give I would not do an MBA at anything other than a top tier school because the value attributed to such an MBA by the top consultancies is significantly lower. If this is for reasons of cost, then it is a false economy.
On another note, if you have over 20 years' experience then you're likely to be over 40, which is very old to make such a jump unless you were to be recruited at a senior level, which is unlikely given that your experience is purely IT-based. Furthermore, consultancies are currently being flooded with applications from fresh grads and the refugees of the banking diaspora.
Sorry if this sounds very negative, but best of luck whatever you decide.