You have narrowed the problem down to the amplification, so if I was you I would forget trying to tweak the DAC. So lets talk about the amps
Do you still have the previous integrated amp that you used? If so try connecting the pre amp of the integrated to the power amps. If everything works then the problem is the new pre amp.
If that doesnt solve it connect the new pre amp to the power amp section of the integrated ..If you get sound then the problem is in your power amps.
If you no longer have the integrated, perhaps look to buy an old integrated or AVR from a charity shop or ebay. It could be old as long as it works. Then use that for your testing