Note from Scott, W4PA, today about the Orion depth: "I measured it today. From the front of the knobs to the far edge of the heat sink is 18.25" depth. Without the front panel knobs (from far edge of heat sink to front panel) is 17" depth. " He noted that the heat sink is the same as on the OmniVI+, so whatever you need beyond the heat sink with the Omni set up, you will need with the Orion. 73, Jim KH7M