This should be the Lumia line-up. Right now, it's too complicated.
Lumia 540 - 3MP Camera, VGA Front Camera, Snapdragon 210, 1GB RAM, 4 inch display, entry level device
Lumia 640 - 5MP Camera, 2MP Front Camera, Snapdragon 400, 1GB RAM, 4.5 inch display, low-end
Lumia 740 - 7MP Camera, 5MP...