Why would 2 schiit aegir amps sound the same as 1?

My setup is forte 3s, schiit freya+ preamp and 2 schiit aegir amps.  They accidentally only sent 1 amp last week so I was able to trial my system for a week before my second amp came and I switched the aegir from stereo mode to two monoblocks. Yes my speakers are high sensitivity but I’m surprised I need to turn my volume dial to roughly the same spot on the dial.  I was definitely expecting more going from a 20 watt stereo amp to two 80 watt amps.  Overall I’m happy with the sound but maybe I just don’t need both amps?

You are apparently buying into the idea that more watts are better. That is not the case unless you have a hard to drive inefficient speaker. My speakers are 93.5 db efficient. The best move I made was replacing a CJ 250wpc amp with a 35wpc amp. There is a lot of good info already given so I’ll not rehash what's been said. But I’m reminded of the guy who puts an 800 HP engine in a Mini Cooper and wonders why ha can’t get traction!
No, I wasn't expecting 4x the audio quality from 4x the watts.  I do hear a difference, it's just surprising to me it's as small as it is.  This is my first stereo setup.  I'm coming from a budget Sony AVR.  I'm actually realizing just how little an amp changes the sound vs how much difference speakers make.  Don't get me wrong, the Aegir's sound better than the Sony STR-DN1080 but changing my speakers gave my a dramatic upgrade in sound while the amp swap was subtle for most types of music. 
"...I do hear a difference, it's just surprising to me it's as small as it is..."

It's all part of the learning curve. An amp can make a big difference but it takes a big change in amps to do it. Buying two amps is not usually effective vs one of the same amps. Now you know. A big power amp with a solid power supply and reserves will be a big step up for you but if you are happy, keep on truckin'. .
@glennewdick the volume control is fine. I set the volume at around 60% for medium listening 
@russ69 are there amps around 3k you would recommend that would make a big difference in sound?