I have have a buddy who has a system similar to mine. We put a preamp in his system and wow, more natural, musical, fuller sound. Put it in my system, no discernible difference. His: Cambridge magic streamer into a Nuforce mcp 18a analog pre to Bel Canto 300m mono blocks to def tech 8080 st towers. Mine: Cambridge 851N streamer to bel canto 500m mono blocks to Dali Mentor 6. Cabling and rooms are different, but still a puzzling difference.
From your and your friend’s experience, it can be concluded that for different dac/systems, the Cambridge, Holo, Bricasti, PS Audio, Ayre, etc included, the general principle is to go with what you hear best with your own ears from your individual systems.