Atari 520ST FTW!
Seriously, I went out and bought one just so that I could play Dungeon Master in 1987. A friend had the game on his 1040ST and let me play it one evening - he finally kicked me out of his house at 4AM after I got to the 2nd or 3rd level. So I went home, got a few hours of sleep, and then was at the computer store at 8AM to buy my own :P.
The 1040ST had a whopping 1 meg of RAM and could hold 2 levels in memory simultaneously; the 520 only half a meg so it had to go to the disc to load the next level every time you went up or down the dungeon stairs. Since it sold for something like $200 less than the 1040, I figured to save $$ at the expense of time..