Use a Node X as a Pre-amp with the subwoofer out.

I am considering getting a McIntosh amplifier for some KEF R3 Meta Bookshelf Speakers that I will also be getting. I only use my Node X with Tidal, period, nothing else, just Tidal.

I already have a Martin Logan Dynamo 800X subwoofer (it's awesome especially with the PBK mic), so to make this work correctly, I would connect the McIntosh amplifier to the Node X at a variable volume and then set the amplifier at a set volume, and then connect the Martin Logan to the Node X because the McIntosh has does not have a Subwoofer out. 

Can someone explain the pros and cons of using a setup like this? 

Currently I am using a Marantz Cinema 40n that does have a subwoofer out on it, and it's great, but I have always wanted a McIntosh amplifier just because. 

Thanks kindly.