Why get the NC252MP with 150wpc into 8 ohms when for 695 from Buckeye you can get the ncore amp that has 350w into 8 ohms (and both obviously do more into 4)?
All your statements about switching frequency and analog sound are nonsense.
Also if the B100 wasn't enough, you could just get the B200, tons of power, I guarantee more than these can put out continuously for any length of time. Multiple hypex options with way more power too. nc500x for 995 with 380wpc/700wpc.
If the 90db sinad someone mentioned is accurate (and I don't know if it is I haven't seen it myself) then this smsl amp is FAR inferior to hypex, topping, or purifi. like not even close.
You say you didn't want to try the purifi amp one user suggested to you because "if it sounds the same as the hypex you're not interested". The reason he's saying that is because the hypex and purifi amps, at least in the scientific terms valued by the mindset of this forum, are both so incredibly good that they are essentially technically perfect amplifiers, beyond the threshold of human audibility. The new eigentacht 2 purifi also has more power.
The smsl amp looks cool but I need to see detailed testing of it.
You also could have gotten a Tripath TA3020 based amp that can do ~200w into 8 ohms and 400 into 4. If you value subjective impressions the Tripath amps were often described as sounding almost tube like (very analog)... but they don't exhibit elevated even order harmonics and have extremely low distortion so who knows what that meant lol. I can say my own TA3020 sounds incredible. Transparent, low noise, very "fast" with all the micro-details and micro-dynamics you could want =P The Tripath solution is DIY (buy completed amp board, completed PSU board, but no case and wires that's on you) but you can get them for say 230-300 bucks a pop depending on configuration (that's for a board AND smps combined, or the option of the board+smps in one). You can also run them in a bridged configuration and get way more power if you wanted. they make great killowatt+ level subwoofer amps for this reason, except they're only rated to 4 ohms in that configuration, and I'm guessing THD is worse in this configuration as is usually the case, probably also the case with your SMSL amps.
I was hopeful about these SMSL amps, but if the 90db sinad measurement is indeed accurate, they're out. Absolutely NOTHING beats hypex, purifi and topping b/la series amps for performance, value, and power. Nothing. Period. Well if you're ok with semi-DIY Tripath is still great. We're only talking 2 zeroes in THD instead of 3 zeroes, but I don't think you're gonna hear that... but they're not necessarily load independent. Nor is the noise floor as vanishingly low, although it's still sufficiently low. But IMO, AFAIK, you can't beat ~$230 dollars for 200w 8 ohms 400w 4 ohms at .1% thd from the ta3020 v4d from connexelectronic where value is concerned.
The most important point though, and your most egregious mistake, is using the LS50 Meta speakers for your use case, i.e. cranking them, blasting them with the doors open, thinking you need multiple hundreds of watts for them. Your amp isn't the problem, your speakers are. Those are TINY PATHETIC ANEMIC speakers and very inefficient, and you're trying to make them do something they were not made to do. As soon as you start pushing the excursion of those TINY drivers their distortion shoots way up, because the woofer cone IS the waveguide for the tweeter... which is why KEF themselves are smart enough to cross them over to dedicated woofers in their real/serious speakers, you know... the larger ones. Have you not seen erins audio corner's klippel testing at various SPL levels, the distortion, multi-tone distortion, and compression graphs? WHY?! You need bigger speakers, more sensitive speakers. Those things aren't staying clean much higher than 86db, they're breaking 3% at what, the next test is 91 I think? Dude come on. Size matters. Those speakers are so overrated it's not even funny. The KEF coaxes have their strengths, I won't deny that at all, great for nearfield, low level listening, off-axis listening where you don't want a narrow sweet spot, fine. But you need to high pass those and cross them at like 100hz which is garbage, you don't want a sub playing up that high there's so many downsides to that setup. Get some real speakers that you can cross a sub to lower, and that are easily another 3db or 6db more sensitive and require half or a quarter of the power for the same volume, and have half the distortion at high levels. Derrrr I need 300 watts because my inefficient 5.25" speakers don't get loud enough... seriously what?! KEF makes great speakers that are a bad value if you spend enough money (blade 2 metas anybody?), but their itty bitty entry level stuff is just a bad value and there's so many better options unless you absolutely MUST have a coax for some reason... even then I think there are better options. At least you didn't get the q150, one of the lamest speakers to ever exist only suitable for surround channels. The LS50 is a nice speaker it just isn't made for what you want, it has EXTREME limitations, VERY early rolloff, no bass and no real output capability, not if you really want to crank it like I do, and like it sounds like you do... it's the wrong pick. It's about 4-16 times too small, in terms of driver surface area or cabinet volume, take your pick.