I'm told the Amara is replacing the Sweet 16 and has the SR built in.
The Amara is a 20" frame-only machine.
The Capri is the new 18" sit down with stitch regulation built into the table (2 sensors, similar to how Innova did it with their sit down and how Juki does it with the Miyabi). It's a much nicer machine overall and has much less frustrating stitch regulation than the Sweet Sixteen.