Sorry to dig up an old post (I was referred here by another ESRI Solutions Engineer).
Xander Bakker: Do you mean that instead of creating a mosaic'd MrSID raster dataset from individual MrSID tiles using GeoExpress, you'd create an ESRI Mosaic Dataset from the individual MrSID tiles using Arc? Then, you'd create the cached map service from this Mosaic Dataset?
Is this just because you prefer the Overview creation controls in ESRI's Mosaic Dataset toolset, or is there a more specific reason ESRI's Mosaic Dataset will perform better than the GeoExpress mosaic'd raster dataset.
FYI: I am looking at this workflow from the perspective of not having an Image Server License, just ArcGIS Enterprise (hence publishing as a cached map service).