New sub woofer not getting enough input

So I have it on my two channel system a Klipsch r-125.I have to run it at about 10% gain to keep from rattling my windows. However it’s a little big for the space so I recently purchased an earthquake P 10. I noticed I was really getting any output and the Woofer was barely Moving. I moved the subwoofer down to my home theater and connected it to the LFE Output. I noticed I had to turn up the game a little bit on my Marantz subwoofer level. But ultimately the thing was great. I was getting massive cone Excursion and the thing was sliding across the floor.


I really want to use this thing upstairs on my two channel system. But my audio research LS three preamp just doesn’t seem to have enough output to probably drive it. I am using the second set of Line level output. I really don’t feel like buying another receiver. I was wondering if anyone has any suggestions for boosting line level. I’ll be taking some measurements this weekend to see what the actual output is.