I think only advantage REL offers with high-level is convenience factor.
I agree using line-level direct to subwoofer is probably a better approach.
Pre-amp (or using DAC direct line-level) to amp -> High-Level connection to Subwoofer -> Drop voltage to match internal line-level of subwoofer.
For sure line-level is more direct, but who knows if you can really hear any difference unless using long runs of RCA cable is having issues with RFI. Line-level using XLR will have advantage over RCA.
I agree using line-level direct to subwoofer is probably a better approach.
Pre-amp (or using DAC direct line-level) to amp -> High-Level connection to Subwoofer -> Drop voltage to match internal line-level of subwoofer.
For sure line-level is more direct, but who knows if you can really hear any difference unless using long runs of RCA cable is having issues with RFI. Line-level using XLR will have advantage over RCA.