How many SHA256 hashes can a modern computer compute?

I want to know the mathematical time required for cracking hashes based off different sets of characters.

For example, using only 7 letter, US-ASCII alphabetic characters we know that there are 26⁷ possible sequences that could be used. Knowing how many of these could be generated by a computer each minute would give me an idea of how long it would take to generate all possible hashes and crack a certain 7 character hash (birthday attacks aside).

For example, taking the number above, if a modern quad core could generate 1 million hashes each minute it would take 8031810176 / 1000000 / 60 = 133.86 hours to find all possible hashes in that range.

Also, how does the new Sandy Bridge Intel chips with native AES play into this?