It should get you a better signal to noise ratio by going direct to the amplifier, essentially nothing gets in its way. The DX3 does approximately 2v which is enough to drive most amplifiers to full output, so headroom shouldn’t be an issue. The passive pre would be unnecessary unless you intend to run the DX3 in DAC mode with fixed output to safeguard your amplifier from sudden full output if you make a mishap with the remote or press the knob on the DX3 one too many times.