Selfhosted

Most major audio companies like JBL, Bose, etc, are putting out linkable speakers. I've got a Bose sound bar which integrates pretty flawlessly with the Google speakers I haven't brought myself to get rid of yet. I've found that, if the logic exists to sync it with other speakers in its ecosystem and an integration for HA exists, you can probably add it to a whole-house setup via music assistant. And you can probably use multiple ecosystems, too (though I'm not certain you can adjust delays across ecosystems... I've never tried that myself, and it's going to be the most vital part of your whole-house setup. My living room, dining room, and kitchen all have to have their delay adjusted by several milliseconds so it doesn't sound like auditory torture when you turn on multiple speakers in the same area. My bedroom doesn't have to be synced, though, since it's far enough away from the other speakers that you don't hear both at the same time.

...okay, yes, just checked and it is, indeed, quite challenging to sync delays across different ecosystems. I'd recommend keeping all your speakers in a single area (e.g. kitchen, dining, and living rooms) all in the same ecosystem and you can change manufacturers as you change rooms. https://music-assistant.io/faq/tech-info/ )

I think you'd be well-positioned to buy a few speakers according to your budget, and add more over time of any manufacturer you like (as long as it integrates with HA/MA) if you so choose. Any of the well-known brands are generally good. I personally prefer systems that don't require an external amp, but that's personal preference. I've been very happy with my Bose stuff, but lots of people love JBL, Genelec, and even our pals at Sonos re: audio quality. I think the world kind of is your oyster here, friend. Do what your heart (and ear) leads you to.