Could Class D really be that good?

I can't speak on the newer chip amps but I purchased a Hypex Nilai recently. To me it is a step above the Ucd & Ncore's I tried briefly in the past. I purchased the DIY model and feel it is a great amp for the money. Subjectively speaking of the class D modules i had tried in the past I found them to be a hair dry..touch analytical & 2 dimensional at times. For the low noise, transparency, power & size I still think the Ncore is a good amp.. especially when you consider the price. If I was still into Surround/Multi speaker movie systems I would be all about Hypex/Purifi modules. 

I tried an Elac Alchemy amplifier built around the older Ucd modules and felt that Class D amp was good for the money. Definitely better than just the basic older Ucd module but I still felt the top end wasn't as good as say a good class AB. Still a solid amp for the money in my opinion, I used a pair of them for almost a year. 

Anyway, the Nilai is definitely an improvement in my opinion. It's hard to describe an amplifier but I just find it smoother & groovier than D's I've tried in the past. I've only used it for a few weeks now but I can't find any faults in it. If Class D is able to improve upon this and keep it at these low costs I think that is a win for a lot of audiophiles. I definitely welcome more builders designing amplifiers around these new modules.. especially this Nilai.  

@lanx0003 I have not listened to the Apollon but I had given it some research. Just on looks & the couple extra features & upgrades I would have preferred that model. But I really didn't need a new amp..was just curious about the newer Nilai tech & power supply. The Stereo DIY was the cheapest I could find & I figured worst case scenario (no difference from Ncore) I could resell it with minor loss. Basically I wanted a taste of the newer tech at cheapest price. Personally I like the look of the Apollon. 

Now that I know firsthand about the Nilai I at least wish I would have gone for the mono blocks. Although I certainly don't "need" them for extra power.

Definitely there are ways to change the sound of these amps with whatever op amp or buffer. There are quite a few selections to choose from depending on the company. Problem is..which one or ones sound best? Is there a popular opinion on which one is subjectively "best"?

Going back to the Elac class D amp I mentioned the input stage made all the difference. I had heard the basic Ucd modules ​but Elac did a Jfet or Class A input driver that took that mediocre module to a new level imo. 

I while back when I was looking at different amps I liked the idea of the VTV tube buffer but it seemed a little pricey & I don't recall seeing any specs for it. My opinion was I'd be better off going with a tube preamp then an add on tube buffer. Which I'm a big fan of pairing Tube pre's with Class D...or really any amp lol. I've experimented with a few different pairings. Tube pre with low power supply noise & a smidge low harmonic distortion sounds good to my ears. I just started & almost finished with a new preamp build to pair with the Nilai. Minimal circuit design & the designer provides specs. Small parts list so upgrading to V-caps, mundorfs, AMRG carbon films & such wasn't too bad. 

I definitely have no experience with op amps but believe in their ability to change a piece of equipments performance. After building the Nilai the first things that come to mind are wanting to upgrade the jacks along with internal dampening. The caps could be a major hassle due to space..the wiring not so much.

As much as I love the beautiful inaccuracies or pleasant mild distortions/coloring of tubes I do appreciate low noise linear solid state gear as well. I pulled a tube pre off the Nilai yesterday and enjoying now straight from dac. With certain music I prefer the visual perceptions I can get from tubes and a clean power amp. Kinda funny how I strive to find & appreciate an amp like the Nilai due to its engineering and impressive specs & then look for different ways to add changes to its sound. Not with just passive parts.