Well, like I said, if your speakers are passive, they need a power amp (or powered mixer). If they're active, they don't.
Here a paragraph I cut and pasted from the link you sent.
"Monitoring Features
Flexible monitoring capabilites are designed to help simplify recording and mixing operations by letting you hear exactly what you want at all times. You can monitor the MD8 with a pair of stereo headphones plugged into the front-panel PHONES jack, as well as with an external amplifier and speaker system connected to the stereo MONITOR OUT jacks, overall output volume is controlled by the MONITOR LEVEL control. The MONITOR SELECT switches let you hear Group signals, stereo signals received at the 2-TRACK IN jacks (such as a 2-track recorder, external submixer or sampler), the stereo output buss, or the cue signal from the recorder tracks. By using the CUE LEVEL controls for each recorder track you can set up a separate monitor mix, thus leaving all eight mixer output channels open for connecting additional audio sources such as external MIDI instruments."