Screen or Storm Doors can be added to any exterior door unit, although sometimes you need what Therma Tru calls a storm door adapter or basically pack out the frame to receive the z bar frame of the storm door. A lumberyard or custom quality window & door supplier (not a box store) should have available wood combination storm and screen doors and or higher end custom metal ones.

Heres the direction I am heading: The opening is actually 35", so I am going to buy 36" vinyl screen door (low maintenance is desired) that is 1" thick. On the latch side of the door, I will route a 1/4" inch overlay lip. This will cover the door/rail seam and act as the door stop preventing the screen door from swinging into the front door. I might put a 1/4 round detail on it. I will buy face mounting "self close" screen door hinges, make 1/4" pads to mount under them on the rail side, then screw them to the rails and the door. The door will extend 1/4 inch beyond the door rails and only take up 3/4" of the 1 1/2" space between the rail fronts and the front door. I hope this will not interfere with the existing door hardware. If it does, I will make the lip and pads deeper to move the door forward. I cannot use the latches commonly available at the hardware store or big box store as these almost all require 1 1/2" to 2" inches to mount. My thinking now is a simple pull handle on the outside, and a push plate inside. I am thinking to use a magnetic catch, a bullet catch or the latch listed below. I may hold off on the catch after I see how firmly the screen door hinges hold the door closed. If anyone has latch/catch ideas, I am all ears! Here is a link that might be useful: latch

My opinion Therma Tru would be the lowest I would go on the food chain. I would seriously consider Provia at the very least for your front door.

A little bit of hyperbole above, but the Signet door is indeed a measureable step up from Heritage and is one of the better doors out there. The "skins" are still outsourced, but the overall slab is assembled by Provia. Paint or stain wouldn't be much of a determining factor if door quality is a concern for you. As far as the storm, for a South facing door, talk to your sales person about the need for venting and/or tinted glass. A storm will protect the door, but it can also be detrimental if excess heat is able to build up between the two.