I'm with you on this. The fewer the boxes, the better, particularly as that snake-pit of untidy cables is expensive and the cable that improves sound has yet to be invented, however costly it is! Something to be said for all-in-ones as modern-day modules for amplifier, DAC, streamer, etc are so small, why not put them all in a single nice case with a good quality power supply unit - and no bloodly cables?
My search started when I decided to move away from tube SET amps. A fellow Avantgarde owner with Trios was raving about his latest and greatest amp purchase - the modest Benchmark AHB2. This was in early days when it hadn't been professionally reviewed, so I just bought it on the basis that if it's so wonderful powering Trios, it should be equally fantastic with my Unos. Big mistake - it was a dull as ditch-water with my speakers, so I started my search.
I hadn't decided on a power amp, or integrated, or an all-in-one for powering my high-sensitivity Avantgarde speakers (then Unos, now Duo XDs), so I asked around on forums for suggestions, spoke to dealers, read Stereophile, etc until I had a short-list that stretched to 12 units. I bought many of these used on the basis I could re-sell them at little or no loss and borrowed others from dealers.
Some were power amps, some integrated and some all-in-ones. I was surprised at the difference in sound between these 12 amps. Some were quickly discarded, but others greatly impressed.
Amongst the best were the 30 watt Class A Accuphase A-36, the GamuT D200 Mk III, the Mark Levinson 5802. Other less satisfactory ones for one reason or another were from Sugden, Bakoon, Valvet, Lyngdorf, Micromega, Quad and Benchmark. However, taking account of value for money as well as sound quality (mostly digital via CD or streaming but no vinyl), I found the modest NAD M32 the best of the bunch, but I later upgraded to the even more satisfactory and astonishing value NAD M33 all-in-one.
I could improve the sound quality but I seriously doubt I could for less than 20K and I still have the option of using a different power amp, or DAC for example with the NAD.
These £3-8K amps may be less that your budget and my chosen amp was amongst the lower-priced ones. £4K worth of electronics powering £34K speakers may sound daft, but I have no intension of upgrading any time yet - and it'll cost a great deal more unless someone comes out with an even better all-in-one. In the meantime, I'm very content with this Best Amplifier, Best Component and Editor's Choice unit from Stereophile's annual awards 2021.
I really liked the Accuphase. Beautifully constructed, thoughtful features such as gain switch and 2 independent speaker outlets, etc, but after prolonged listening I found it slightly too polite and slightly lacking in dynamic excitement than I was looking for and which I knew my speakers were capable of.
All I can suggest is that you make a short-list, buy (ideally used) or borrow all of them and give each a proper opportunity to impress with your speakers in your room. Results may well surprise and you won’t end up with a system that unbeknown to you could sound better with a different amp from your short list. Happy hunting.