With the digital amps they're using now, they can cram them into about any head unit, plus the rest of the circuitry has shrunk in size, allowing more room though with more processing compared to years past... But yes, true "deadheads" or preamp only units are far and few betweeen.. just the drz9255 and the P9 come to mind.. I remember even the Excelon's had one deadhead "SQ" unit.. That's going back.. I had one.. actually two of the same model because the ribbon cable issue with their faceplates.. stunk.. Killed both units.. shameful! Sounded killer before they died though.
The 9887 has a "Power IC OFF" function to kill power to internal amps and better SQ.. page 26 of the 9887R (non-US) manual. I imagine or would hope it's a feature on a lot of their HU's but maybe not.