I kept my old Antec full tower (26") ATX beige cases in perfect condition. Just open the fan holes to 120mm or 140mm, and the side panel to 200mm, and I have instant retro that is usable for modern cooling. Love them, plenty of room for cooling choices or for addition of various do-dads that become popular like liquid coolers. And they have those darn cute feet you can turn out, gals love them.
BTW, you can purchase hole cutters from electrical or plumbing supply centers for making 80mm or 92mm holes into 120mm or 140mm holes in soft sheet metal easily or use a dremel abrasive saw if you are confident. The hole cutters are pricey, but if you build a bunch, it is worth it. You can use them for off center holes from the previous ones that were smaller. Possibly look for them in estate sales from craftsmen as they rarely become dull on the cutting edges. The hole cutters are preferable due to the edges being less cutty on skin, since they are bent inward at edges after punching out.
Right now, the black Antec 302 built off the older Antec 300 case which was meduim tower full ATX, is the one to use for us older builders who have been building since the middle nineties with the celeron overclocking. The latest 302 costs about 70 full retail USD + shipping. They weigh about 15 pounds and heavy guage steel relatively, and built like a tank, I have built around five with that case. I wish I had bought more when they were on sale. I am not very prolific builder like some, mostly for friends and family, but research every day for hours to keep up on latest developments.
The 302 has USB 3.0 in front and filters on power supply input fan area on bottom of case, otherwise similar to 300 except for front fan cages seperate from case, mild changes. Antec listens and they are still available in some stores online and Fry's.