When installing a chimney liner, getting the liner through the damper opening can be something of a challenge. A typical 6" round liner is 6.25" on the outside diameter. Your damper opening is probably in the range of 5". There are generally two ways to get around this problem.
Simply put, convection stoves heat the air, where radiant stoves will heat nearby objects. You'll want to choose a model that is primarily the type that will work best in your situation.