Given that you already have 2 channels of power amps that can drive speakers with major impedance dips and low to average sensitivity such as B&W's, your weak links are obviously the following, in order of significance, but in my opinion only:
1. Quality of the recordings you played - Keep in mind if you listen to rock and pop bands, the musical instruments such as electric guitars, bass, keyboards already involved electronics that may or may not be as good as your media players, preamp and amps, and then through more electronics such as mics, mixes, equalizers, preamps etc., just to name a few. Classical music recordings would be better for comparing electronics imo, and some jazz types are good but not totally immune to the electronics contribution upstream.
2. The RX-A2040 - It is a very decent AVR, but it's internal bottleneck is likely the volume control chip that is based on a LSI (large scale integrated chip) that has to do a lot of things all in one chip. I have posted a linked to an article on this a few times on this forum. This is just based on specs, I don't think the effects are audible, except to golden ears, or some genuinely sensitive ears/brains.
I don't even believe there is any audible difference between with and without the Emo amps (to most people I would think) at low to moderate volume in a small to medium room sitting within say 10-13 ft. Obvious it did to you, so that's great, one problem solved.
Aside from the electronics, as others have pointed out, your speakers and room acoustic conditions probably have the most influence on sound quality you perceived in your own room. Take a look of the following FR graphs for your 683 and the presumably improved 683 S2. If you read the full reviews, not that their impedance characteristics are not good (not shown) either, but your big monoblocks have you covered so no worry there.
I think the 683 could sound very good to some people, but if you are the type who prefers neutrality and accuracy, some of those speakers Ryan recommended may sound much better to you. Just don't under estimate the importance of the quality of the recordings. Garbage in garbage out does apply...
B&W 683 -
https://www.soundandvision.com/content/bw-683-surround-speaker-system-measurements
The reviewer noted:
The vertical responses shown in Fig. 2 strongly suggest that you avoid listening positions significantly below tweeter height.
Fig. 1: B&W 683, pseudo-anechoic response, off-center in the horizontal plane, at 45° (red) and 60° (blue).
Read more at
https://www.soundandvision.com/content/bw-683-surround-speaker-system-measurements#k0RdKiD1fUD7EbL2.99
View attachment 30521
Fig. 2 : B&W 683, pseudo-anechoic response at 15° above (red) and 15° below (blue) the tweeter axis.
Read more at
https://www.soundandvision.com/content/bw-683-surround-speaker-system-measurements#k0RdKiD1fUD7EbL2.99
View attachment 30523
B&W 683 S2 -
https://www.stereophile.com/content/bowers-wilkins-683-s2-loudspeaker-measurements
The reviewer
View attachment 30522