Two subs

[Venere]

I currently have a two channel system with floorstanders running full range and a REL sub for bass reinforcement that I use mainly for music with the occasional movie. I was pretty surprised at what the REL did for soundstaging and tonal balance, and I keep hearing that two subs are better than one and i love symmetry so i am probably going to buy a second REL. I know everything is room and system dependent and I will need to carefully integrate the second sub , but could those of you who have gone the multiple subs route tell me if you generally reduce the volume on both subs versus a single sub (which seems pretty logical) and if so by how much? Just a little? By half since there are two subs now? Just curious what to expect when I start the setup. Thanks as always.