Since I got them for back surround together with the ES55 and my S30, I have a clearer picture to tell you at least 2-3 different scenarios. It was hard not to put them in the front as well, they have excellent bass.

Scenario 1. The ES20s can easily function as an independent entry-level hi-fi setup, for example with a Yamaha 201/202/301, etc. You will definitely enjoy sound even without a subwoofer, and for those who have vinyl in the game, it's a sure recipe with the Audio Technica LT120 and its variations. And when we talk about sound, we mean something you can't get close to with ready-made systems and multimedia PC speakers. I wouldn't say they belong to the iconic audiophile category because Polk has the Legend series for that, but the good thing is that these speakers play ball and are often compared in the serious categories. They have respect. If you're considering them for use as right and left, they will surprise you. The floor shakes, and the highs are crystalline. I believe that with a separate subwoofer and the ES20s in front, you'll fall in love for life.

Scenario 2. The ES20s as rear surround speakers are capable of scaring you because they really approach 45Hz with ease, and here I don't know many two-way speakers of this size that have such range, so if you already have front towers with strong woofers (the S55 and S60 easily go below 35Hz) but without a separate subwoofer, and you give full range to the rears as well, then the roar behind you will send you... I put them on a V6a A/V and heard one of the best Atmos experiences. My personal preference is to set the center at 80Hz and above (even though the S30 is a multitool in any position and use), leave the rest as they are.

Scenario 3. Sound! Their reputation says they are the most respectable VFM, and I can say that from a sound perspective, it's good and doesn't just give the impression of "good for the money" because to get something a bit better, you'll probably have to pay double. The bass management is remarkable, the floor will creak when needed, and the highs will make you turn your head toward the direction of the sound. The presence of the stereo soundstage is wonderful; their sound generally doesn't come out as warm as the big towers (ES55, 60). Pair them with Yamaha amplifiers as most do, and there are plenty of comments showing that owners who switched to Yamaha with these speakers saw a resurrection.

Additional details. The ES20 has the same dimensions as the ES55 except, of course, for the height, but not the same width compared to the ES60. I attach a picture so you can understand, because I enjoyed this. So, if someone doesn't want double woofers in the front like me and has gone with ES55, they will find that the ES20 is a better match sonically, aesthetically, and construction-wise than going with the ES15, which is noticeably smaller. For height use, go with the ES10, which is small and delivers more than your amplifier can communicate to those channels. Finally, for listeners who want bass to caress them, with great extension, they can set up, as I said before, a 2.1 with ES20 and an HTR12 and do everything in one, music and movies. For me personally, since I have the whole set except the subwoofer, I will take a while to get a subwoofer because the front towers alone are almost shaking the window frames in the living room.

Conclusion, there is no way you will regret buying the es20 whether it is for an entry-level hifi setup, a 2.1 all-in-one setup with es20 and hts12 subwoofer, or for a 5.1 setup using them as back surround speakers.

P.S. Forget about the hts10, it is neither value for money nor that good because it has obvious compromises compared to the hts12.

Perfect, excellent speakers for their size!!!
Quality construction, excellent finish, fantastic design!!!
Full, powerful, clear, and crisp sound at any volume level they receive from the amplifier!!!
The bass is so intense, clear, and clean with amazing "spread" in the room, thanks to the innovation of the "Power Port", that on my amplifier I have reduced it to -2 and you can still feel it.
Mids and highs are clean and also clear.
I drive them with a Yamaha RX-797 with 2x100W power at 8Ω.
Amazing purchase even as used!!!

The sound of the POLK S-20E is a combination of lushness/sweetness, musicality, revealingness, and neutrality.
The midrange is simultaneously full-bodied, airy, and analytical. The highs are extended and airy, while the bass is effortless, unobstructed, and goes very low. Thanks to the patented POWER PORT technology, the behavior of the drivers is impressively natural, clean, and undistorted.
The speaker is extremely enjoyable, revealing, and impressive, and it performs well with all genres of music. The difficult part is finding any flaw in it.
"George Barry"

Simply wonderful. Full sound at all volumes, they utilize their capabilities with a good amplifier. The price is their only drawback, guaranteeing the American sound.