Very early DOS titles tend to be quite speed sensitive and will only run correctly on a 4.77 MHz PC.
There are a number of good 100 % IBM compatible XT clones that you can also look at and that might be easier to source than an original IBM PC (model 5150 or 5160).
Many later XT clones were actually Turbo XT's since they utilised an 8 MHz or sometimes even a 10 MHz Intel (or AMD) CPU that could be slowed down to run at 4.77 MHz.
Just try and avoid any clones that utilises an NEC V20 CPU, since those CPU's sometimes tend to run slightly faster than the original Intel/AMD CPU at the same clock speed.
For this era type of PC, a CGA (and an MDA/Hercules) card will be the most suitable.
You don't necessarily need an original 5151 and/or 5153 monitor - any clone should suffice (once again, since they might be easier to source).