Have a look at the Aeron chair (I sell them :-) this is an amazing chair as you do not sit in it , you just float in them . You can just google there is millions of blogs on them .This is the only chair that come in 3 sizes to fit different body types. Also the combination of the sit and stand desk is a great choice you made as our body's is not actually designed to sit down for long periods, so new studies has found in the ergonomic fields.