The reason for the searching for another model with the same design is because you are wanting to put something inside the case that there isn't quite room for it. Such as a radiator or extra long video card or additional water cooling parts or you may want a bigger window.
There are two ways to go about creating more space inside or creating window space.
1. If your the handy type and are not afraid to take things apart or remove something or cut something.
2. Have someone else do it but that will cost you more then what you may be willing to spend. Some retailers and manufacturers will offer custom work and there are places that specialize in custom work. An outrageous place that comes to mind is ; www.mnpctech.com
For this tutorial we will concentrate on the DIY type and let's say that you bought the Cooler Master HAF-X Rc-942. Now this case is huge and has many , many options for fan placement and other cooling options. You might say how could you possibly want anything else in a case with all the stuff that this one comes with.
If you are into water cooling and you are cooling the CPU and Video cards then there is not a huge need for fans to have a good air flow , one in the front (230mm) and one in the rear (140mm) can supply a good air flow.
So with that said there is not a big need for the (200mm) fan in the side panel and you would rather have the side panel one big window instead of the half window that it comes with.
So what do you do ? Customize !
Tools needed , small drill and metal drill bits, a Dremel tool with metal cutting bits and a bit to cut trough plexi glass., screws and nuts to attach the plexi glass or a roll of double sided tape. A full sheet of plexi glass it usually comes 480mmx480mm, about 6' of small rubber chanel strip for the cut edge and to make it look neat.
Measuring and cutting.
If you opted for the expensive Cooler master panel then you want to measure according to the window size and mark it where you want to cut. Do not cut the exact size of the window as you will need the window to be attached to the side panel. The red markings will give you an idea of where to cut and you either want a square window or one with some design to it.
You can also visit your local hardware store and get a sheet of Acrylic and just cut out what you want for a window leaving the window about a 1 to 2 inches bigger then the opening for a border around the inside to attach the window to the panel.
The double sided tape will hold the acrylic and make a clean look with no screws. you can use screws if you chose to.
Getting the right parts and making the cuts carefully will give your case a professional look like you bought it that way.