Ideas of how to connect a pair of Revel Performa 3's to a Marantz PM 10?

I purchased a Marantz PM 10 Integrated amp due to down sizing recently.  I kept my Paradigm Persona 3F speakers and a Pro-ject 10.1 turntable.  The idea was to just have a nice 2 channel simple system.  That works great, however, I also have a pair of Revel Performa 3's subs that I would like to use with certain types of music.  The problem is the only output is the Recorder Audio Out.  I know this would be a fixed output and therefore would have to adjust the volume and crossover from the subs every time volume on the amp was changed.  Generally, I would not be changing the volume level once listening.  Could this damage the amp or subs?  Is there another way to connect these subs to this amp?  Oh yeah, I am 70 years old and obviously not as sharp as I once was, hence not being thorough has led to this dilemma.