Today I received it, I won't go back to not having a sub.

For those who are thinking between this and the 10, let me tell you that as soon as I opened it to try it, my housemates who were in the next room got scared and started yelling at me as soon as they realized I was the one making the noise.

I have a small room (3x2.8 with a height of 2.6) and the walls have no soundproofing reinforcement, just a simple door, etc.

I set up the sub on its own because I forgot to get a second RCA, and as soon as the drums started, they woke up from the couch thinking someone was banging on the walls :)

It was set to high sensitivity by default and I had it below 30%. Now that I set it to nominal sensitivity, it's just fine, and I can even turn it up to halfway without the walls shaking.

I have no idea about comparisons with others, but I know that I already like it a lot and I intend to keep it.

I haven't even dealt with the placement and setup yet, and it's already a huge upgrade from the Kali Audio LP UNF.

I haven't tested it, but I definitely prefer a 3-way system with a sub rather than getting big 8s for the desk. Also, good luck with the vibrations that will be created from the speakers in an office setting. The sub is further away and completely out of contact, so it seems to be quite better from that perspective.

Another plus is that you have much better control over how much bass and how much volume you want separately from each other without messing with the frequency response.

That's it; I might come back when I have a more complete opinion.
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After using it for a while, I have to say that now the speakers I liked so much before are no longer the same as before. I let them play on their own, and you could tell that the sound was coming from two speakers in front of you.

With the sub, the soundstage opens up, and you feel like the sound is coming from "everywhere." Also, my 5-inch speakers struggle to produce all the bass, and I now understand the "roll-off" that they have.

The whole system sounds better due to the crossover that cuts the lows, something I heard before, but now I see what they mean.

This isn't so much a critique of the KRK since it's my first sub, and I haven't heard others in my space.

What I know is that it has all the necessary adjustments with switches on the back and such, and a ground for grounding (which I didn't need, as I don't hear any hiss with the cheap RCA I have). And generally, the build quality, price-performance ratio, etc., is very good.
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Note: No one has complained to me all this time. I listen at normal volume, not loud, and it's just fine; anyway, you don't want to turn it up louder than the speakers (and it has plenty of volume if you want) and always depending on the space you're in.

If you set it up correctly, you won't disturb anyone

Performance/Price ideal for anyone looking for a subwoofer.
Nothing more, nothing less.
Best in slot.