I run sans pre-amp with both my DAC's going straight into the Maraschino's. I can't imagine wanting to change that layout anytime soon. Are you looking to upgrade from an existing pre-amp, or wondering if there are benefits to adding one?
My NOS Metrum mini quad dac has no volume control like your Benchmark DAC2. But now that you mentioned it... If i would buy a new DAC it could be smart to have gain control built in. It is a component less and also makes the wire path shorter.
That aside, my LDR based EVA II passive doesn't go or do loud that well with the Maraschinos. The volume goes to "23" and the step from volume setting "22" to "23" is to huge a difference. It sounds pure and detailed but highs can be a tad on the hot side compared to the pre amp stage of my Dussun V8i. The pre amp stage of the Dussun also sounds a bit more musical but slightly less detailed. It's a bit give and take with both.
I can't/won't hold on to the Dussun V8i to only use the pre amp stage on this big amplifier. And the EVA is about fine for now for the room i'm listening in. But i'm going to move to a bigger room with bigger speakers in the future and then the volume issue will only get worse i suppose.
I still have an intrest in passives and the LDR from Tortuga Audio caught my intrest. I wonder if the volume has to be way up with the Tortuga one to as with my EVA.
But i think that particular question would be better asked on the Tortuga forum.