The 3688 refers to the Morex case that comes with that system.. The power supply included is just a regular DC power supply.. You'll still need to add some kind of power regulator or ITPS.
The OPUS comes in it's own custom case and is regarded as a superior power supply/case combination. This power supply has a higher output (for more devices), and I believe it already regulates power and provides for automatic shutdown control as well (so no need for ITPS).
If you've got the cash, the opus solution is better.