An a3000 running Dread (https://youtu.be/vj-GVCcd4yo?si=X_R_f0TEnPHqOvVv) would be quite something!
What I'd love to see would be an Atari ST + T212 combo running doom (my electronics skills are not that good).
Also take a look at quake on the gba - 16mhz arm with cache. https://youtu.be/R43k-p9XdIk?si=yDycN7I3I4NWvEgU