best dos machine

i have been thinking of running a good dos machine or finding one. i find that each machine is different from the hardware to the way it runs the software. some have the use of a hard drive and some don't i have thought of wanting a sorta high end dos machine one that has the use of a hard drive and can run any program that dos can run and not have issues. i remember with dos some programs would run to fast on some machines but with others they would run just fine or to slow. around in seattle its hard for me to find a good dos machine since most of the older machines that became unwanted got sent to a computer ecycler where it got stripped down and killed off for free or that the store sells the stuff for more then what its worth as a whole. maybe one of you might have something or know some stuff.