The case there doesn't look like the DeskTopper system I knew, but this is going back a long way (well, to the 90's anyway). Using a PC case would be cheaper, and I imagine fairly straightforward - unless like me, you are hoeplessly clumsy at small fiddly tasks with your hands. Main thing is you wan tot keep your Atari keyboard, recasing that will be the problem, though bodging is always on the cards
Alternativly, it's fairly straightforward to modify the Atarit o use a standard PC keyboard, and to be quite honest, Atari's own keyboard on their 16/32 systems aren't great anyways, in my view. A bit "stodgy".