You could probably get away with just using a 2-sample t-test (http://en.wikipedia.org/wiki/Students_t-test#Equal_sample_si...), no? No sense using a non-parametric sledgehammer unless absolutely necessary :).

Actually, just looking at the variance of the columns tells the same story as you've discovered above:

> var(data) A B C D E F 117.19610 20.49239 33.13114 90.62195 115.39044 27.34298

A, D, E are in the same group, B, C, F are in the same group.