112RD100 vs 112RP100 volume level

can anyone tell me if the volume output (that is clean headroom) would be materially different for the RD100 as compared to the RP100? I have one of each sitting side by side and trying to determine if there's something wrong with the RP100, which aside from the lower output volume sounds very good.
thanks,

I would say the gain stage in the rd-100 is going to make it louder,even if the amp is set to clean it's still running though that gain stage,some have tinkered with different op=amps and cap values to get the best of both worlds out of the rp-100.