Most likely it is rated at 1 or 1.2V. This is pretty much standard. Even the high end AVR's/pre-pros offer the same i.e 1-1.2V. And that is at full volume with a lot of distortion. Like I mentioned before, at moderate listening volumes you may only get like 0.6V. You can multiply 0.6V by the amp gain to get the voltage out of the amp. Emotiva amps have unusually high gain like 32 (not DB). So 32*0.6= 19.2V. That gives a whopping 46W with a 8ohm load
No wonder people don't notice much difference with a separate amp and AVR as pre-pro. Don't believe those who make euphoric claims that they hear things they never heard before when they added a separate amp and that the bass is deeper and tighter. It is all in their head. Your brain wants you to hear new things just because you spent on a new amp
I also tried the Emotiva UPA-2 (older model) 2ch amp with my RB-81's driven using the Yamaha RX-V663 as pre-pro. Absolutely no difference.
You can try a bump box like Samson to bump up the pre-out voltage from the AVR. I tried this with the Rotel RB-1080, Yamaha RX-V663 and I could play my Magnepans louder. It basically bumps up the AVR pre-out voltage by a few db. Though I didn't hear a lot of distortion, I didn't like the idea of using a $50 bump box on a $1200 speaker. More cheaper devices in the loop leads to more noise/distortion.