I am a door and window dealer. Home Depot and Lowes will usually sell stock items for less than I am willing. If the item is special order I can easily beat their price, but more importantly I go to the jobsite and I confirm dimensions and code compliance for no additional cost. Windows and doors can be very complex and expensive and they cannot be returned. This is an area where unless you have had a bad expierence you cannot fully appreciate the value of that service. If the cost from a window specialist is even close to HD or Lowes it's a no brainer. After all if you can't trust them to mix paint correctly how can you expect them to understand Egress codes, Jamb widths, Sight lines, DP ratings, Solar Heat Gain, Structural mulls, flashing details or Temper codes. All of these details must come together in order to ensure a proper fit not just in the opening but in reference to the application. Vinyl windows are not as tricky but they still require more knowledge than their employees usually have. The simple rule of thumb for the big box stores, if you know exactly what you need and where to find it on the shelf, buy it and you probably saved some money. If not, find a professional that you trust.

Just a few thoughts... R value is not the best measurement of a window's energy performance. U value is a much more accurate measure, but unfortunately most window sales folks still use R value in their presentations because most people have been conditioned to think in R value. LowE is a metallic coating that is applied to one (or more) lites of an IGU (Insulating Glass Unit) or thermo-pane window. Not all IGU's use LowE coating and not all IGU's use an aluminum (metal) spacer. The top-of-the-line IGU's manufactured today use what is called WET or Warm Edge Technology spacer. There are several different WET spacers in use today, including a couple that are stainless steel based. LowE coatings substantially increase the energy efficiency of a window. LowE coatings are required by energy code in many parts of the country for new construction. Having storm windows is better than not having storm windows, but the energy performance of a single pane window with a storm window is not comparable to a modern IGU-equipped window with LowE and argon fill. There really is no comparison in energy performance numbers or actual field measurements. John, you have classic old windows that might be worth saving for the asthetic value, but you will lose something in energy performance if you do so. I really like older windows, personally, and if the original windows are in good enough shape to save, I would attempt to save them...but that would be a trade off in performance versus new windows. If you can afford it, you can get newer windows that look every bit as good as the originals with much better energy perfomance. Something over 70% of all LowE coated residential glass in North America is manufactured by Cardinal Glass which happens to be headquartered in Eden Prairie, Minnesota. They also happen to have an R&D lab in Minneapolis, which is a local phone call for you I assume...Cardinal supplies most of the major window companies in North America with LowE glass and also many of the big window companies with IGU's as well.

From the photo - That is not black trim. That is the storm window frame with a black accent paint around it. I can guarantee you that when you remove the storm window, the fin of the aluminum window beneath it will not be exposed. With vinyl siding, it is NEVER correct to install exterior trim on top of the siding. I don't know what your original siding was, underneath the vinyl. Do you? But with aluminum windows, I can almost guarantee you that the siding butts up against the window frame. IF there was a casing trim of some kind, it was most likely removed when the vinyl siding was installed. You remove the storm window. Then you remove the sashes/glass and mullions (if any) from the window, leaving just the frame. Then you pry the frame into the opening, pulling out the nails. You also hope at this point that the vinyl "J" channel was not nailed through the window fin. If so, the "J" will come off with it. When the frame is out, you then have the opening you will be dealing with. You can have the new window made to slip between the "J" and cutting back the sheetrock, or you can have the new window made to fit sheetrock to sheet rock, and trim the outside appropriately. You'll be able to see where the studs are, and the window cannot be bigger than the rough stud to stud opening. The problem is the vinyl siding. I hesitate to recommend cutting that back. Perhaps someone else here has a suggestion on how to do that without risking cracking/chipping and ruining the siding. The other problem with cutting it back to reveal the window fin is that you no longer have the right "J" channel - though maybe they can find some and slip it around the siding cut. But then you also cannot nail it properly after the fact. This is why I recommend leaving the "J" and siding alone. What abosolutely MUST be done in your situation is that the proper drip cap/flashing MUST be applied above the window. It must go up behind the sheathing, and turn out over the window, extending past the "J" channel, and then a downward bend of app 1/2". In your case, you have to have someone custom bend that on site. The addition of vinyl siding will make any pre-made drip cap unusable. It must start from up behind the sheathing or original siding, NOT the vinyl siding. Also make sure that the new windows are fully injected around the frame with low expanding insulating foam. This will be an absolute must for your application. That's probably clear as mud. But I did my best for you. Keep in mind, this is a standard every day job for any competent window company, and I did thousands of windows like this that never leaked. But if you get a crew in there that takes short cuts and depends on caulking for shedding water, you're going to be in big trouble down the road. Hope that answers your question. What the other guys here said is more true than you can know. "Contractor" guys are clueless about this kind of stuff, and it shows in the end results, and we've seen it a million times. I also want to tell you that if you chince on this, you will get a chince result and look. The money has to come out of somewhere. You don't want it to be the product or the workmanship. Pay for a good job done right, and you won't be doing it again in less than 10 years. Ignore this advice, and you will. It's not an insult to your intelligence, which I'm sure is adequate. It's just the fact of it. And unless you do this for a living for years, you cannot know, and I don't mean to offend, but that's the reality.

Double pane laminate with LoE coatings would be your best option. However, I suspect that the installed cost would be close to what you could just replace the entire window for.