I know that there are a lot of machines (Domestic) machines that can handle heavy duty sewing but for their purposes, I would suggest a good used commercial machine.My mom used to be in the reupholstering business and trust me, you do not want to use your good sewing machine for reupholstering (even though it can be done). Industrial machines can handle greater stress and use heavier thread to make the strength last longer.Maybe you could help them search one out.
Just decide on a machine that you feel comfortable with for yourself. The only way to know is to have someone demonstrate and you try it out for yourself. Another thing I feel is important is the service the dealer or maker provides. Do they offer free classes on how to use the machine? What is their service policy? How easy are additional parts procured? Are they expensive? Just a few thoughts. I personally stand by Bernina and Viking and have heard a lot about the new Janome but ultimately, it is up to you.