One option for grinding grains and beans is also a Vitamix. They have a separate container made especially for that purpose. I think it's good because then you don't have to have a piece of equipment for only one use... this one is very multi-purpose.
I have had a Nutrimill for 2 years and it is terrific. I grind mainly gluten free flours. I have done garbanzo, navy bean, fava, lentils, buckwheat (wonderful gluten free flour, very versatile), quinoa, amaranth, rice, and soft and hard wheat.
The Nutrimill can be cleaned and used for both gluten free and non gluten free.
I used to have a stone mill, but it was not suitable to use for both. Also, the stone broke and was not replaceable, so it was a very expensive useless gadget after that (it was a Hawo).