Hi there! Welcome to the forum
No surprise, you're going to find a lot of praise for the Ascend Sierra-2 on Ascend's own forum
But this is one, rare instance where the praise has little to do with brand loyalty or blind faith. We're a pretty critical group around here, and there are a lot of folks who have become forum members only after a lot of research and trial and error, and ultimately finding Ascend to have been their best choice.
I can't comment directly on those particular B&W models. I have heard the KEF LS50, but only in a store. I have never done a direct A-B comparison for these contenders, so I can only be so useful, and I can only offer subjective impressions.
To begin, Ascend's Sierra Towers RAAL and Horizon RAAL are, quite simply, the best speakers I have ever heard. Their level of realism and resolution is just uncanny, thrilling, and can frankly be downright eerie sometimes. I have a memory of only one other speaker that I would say was possibly even more resolving, and those were the Focal SM11 professional monitors in a professional mastering studio. But those really were "workhorse" speakers. The goal with them was to simply convey the most minuscule changes being made to the mix, and that they did! But in terms of listening to the final product, they did not have the Sierra Towers RAAL's realism. Every tiny detail of the sound was audible with the SM11, but that didn't necessarily translate to realism. It was more like looking at the world through a microscope: certainly useful for mixing and editing, but not the natural, realistic sound of the Sierra Towers RAAL.
So I mention all of that in order to give you a starting point for understanding what the Sierra-2 offer. To start, they are not
quite the equal of the Sierra Towers RAAL, but they are FAR more similar to Ascend's flagship towers than they are different.
The overall timbre and tone of the Sierra-2 are remarkably close to the Sierra Towers RAAL. If you were to hear them separately with some time in between, you would swear they sound identical. It is only via a direct A-B comparison with instantaneous switching that I spotted any difference. And it was a matter of "shades", not "colours". My subjective description is that the Sierra-2 can sound like a real live person is talking to you in your room from 6 feet away. The Sierra Towers RAAL move that same person to within 3 feet. It's the nth degree of clarity and resolution that the Sierra Towers RAAL bring to the table over the Sierra-2. But what you should take away from that is just how remarkable the Sierra-2 really are! They do not supplant or completely equal the Sierra Towers RAAL, but they sure do come as close as any bookshelf form factor could hope for.
In comparison to the KEF LS50, the clarity and detail offered by those KEFs sounded very, very good and pleasing to me. The tone and timbre are not the same as the Sierra-2. For that simple reason, it's entirely possible to simply prefer one over the other. Without the actual original sound that was being recorded being in your room for direct comparison, it's basically impossible to know which timbre and tone are closer to the original.
But I will tell you this much: the realism of the Sierra-2 remains superior in my opinion. I put faith in my instinctual reaction. We have all had the realization that we are able to recognize when sounds are being played through a speaker vs. when they are the genuine article. It can be awfully difficult to explain precisely why we are able to make that distinction. What measurements show it? What technical factors are involved? That's a heady discussion that still draws a lot of debate. But we can all agree that - somehow - we know when it's a speaker, and we know when it's real life.
Well, the Sierra-2 blur that line better than any other bookshelf speakers I have heard. Like I say, I've only heard slightly better from the Sierra Towers RAAL, and it was honestly a more of a sense of being physically closer to the original sound source vs. the Towers RAAL sounding real while the Sierra-2 sounded more like speakers. Both sound very realistic, the Towers RAAL just sound like the real person is physically closer to you so that you can practically hear their eyelids when they blink -- haha.
The LS50 simply didn't have that level of uncanny realism. Again, I only heard them in a store, and not in a direct A-B comparison to the Sierra-2. But real sounds real. The LS50, while very clear and detailed, still sounded like speakers.
In terms of the features you are after, the Sierra-2 should fit your desires perfectly. They excel at lower volumes, remaining utterly clear and intelligible. And yet they LOVE to sing out. You can't help but want to keep turning the volume higher and higher because there's just no distortion from them. Their bass response is wonderfully "tight" and accurate. This is occasionally unexpected for listeners who have grown accustomed to bloated, "slower" bass. It does not reverberate and sound like ridiculous car audio the way a lot of people seem to prefer. Instead, it's realistic, clean, and pops you in the chest rather than vibrating everything for minutes at a time. Simply put, it's how bass is supposed to sound, but that's not what everyone is used to or expecting
Your associated equipment should be completely fine. The Sierra-2 do not require copious power. Like I say, they excel at low volumes. But they can certainly handle and thrive on several hundred Watts if you ever want to have that on tap! Again, like I say, you can't help but want to turn them up
So that's my take. I completely agree that giving them a try is highly recommended. I really, really do not think you would be disappointed.
Hope that helps!
- Rob H.