I would have to disagree with higher cpu frequency is better, unless you are comparing the same amount of cores. Remember, Microsoft Excel and Acess take full advantage of multiple cores, so an Intel P4 at 3.0Ghz would not be better than a AMD Athlon II X4 620 at 2.6Ghz.
For Microsoft applications, I would go with a slower multiple core cpu over a higher frequency cpu with less cores.