Dimensions are 36" tall (without any optional base), 8" wide, 8" deep.
Using those dimensions, I threw the panels into cutlist optimizer just to show you what a cutlist could look like. This is of course the most basic assembly. An example of modification to that layout would be cutting a rabbet into the top and bottom panels, which would expand them out to 8" by 8", and shorten each of the upright sides, by the combined thickness of that material remaining on your two rabbeted panels, or shortening the sides to 34.5" and expanding the top /bottom panels out to 8" by 8" without a rabbet. Of course you could also add a rabbet to two of the vertical side panels, which would also change the side panel dimensions, but of course all of those changes are minor, and would have no drastic effect on your materials used.
You are using just over 1/2 sheet of 3/4" MDF. What doesn't show in this cutlist, would be any internal bracing. I don't know what the original plans called for, if they were corner braces, cross-bracing rods, or interior panels with holes cut, similar to X-static or X-CS.
Without knowing that detail, If I were building for my own purposes, I'd cut 4 more of the 6.5" x 6.5" top/bottom panels for each tower, and cut around a 5" to 5.5" hole in each of them, and use them as internal braces. They would essentially get cut identical to the top panel but possibly using a slightly smaller hole than the 5.75" needed for the driver. 4 of those braces per tower would get spaced approx. every 7 inches. Using 3 braces per tower. would give you spacing of approximately 9 inches, measured on center, which would also probably be adequate.
The cabinets call for 2" diameter rear-port, just above the binding posts.
Hopefully that's enough to get you ballpark of size and cabinet materials.
