I think what blew my mind the most was the imaging (I think that and not soundstage, not really clear on the difference still)
So, look at soundstage as the overall size of the sound from left to right, front to back, and height whereas imaging is more placement of individual elements within the soundstage. When you have a system capable of fully fleshing out these characteristics and your speakers are positioned well there’s the appearance of what’s frequently called a “3D soundstage” that allows you experience more of a performance rather than just flat reproduced sound. This is precisely why I recommended experimenting with speaker placement earlier.
I don’t think I quite understand how ht bypass works.
No, you pretty much got it right. The big question is if the RCA connections labeled “Audio” on your AVR are preamp outs — it’s very annoying Yammy is so vague about this so you need to maybe call/email Yamaha to see what this actually is. If it acts like a pre out then you’re correct — the pre outs from the AVR go into the HT Bypass input on the integrated that is then hooked to your speakers. So to switch between HT and dedicated 2-channel with the AVR completely out of the signal path you just change the input on the integrated — that’s it and it’s a beautiful thing.
As for an integrated, I’m with you on wanting separate components for DAC, streamer, and amp, but in your case you need upgrades in all three and there are some options out there that can do all three for you and leave you the flexibility to upgrade individual components down the road as funds allow. Toward that end, I’d be very tempted to look at something like a used Hegel H190 or H120 as you’d instantly get major upgrades in amp, DAC, and streamer that I think would provide a huge increase across the board in performance immediately in one shot. Incidentally, I’d forgo an onboard phono stage in an integrated amp as the phono pre is critical and almost always an afterthought and severely compromised in integrateds — I’d definitely just go separate there.
Last, I’m not surprised you spend most of your time listening to your turntable as you’re currently streaming Spotify through a Sony PlayStation — EEEEEEEK!!!!! You should at least do a free trial of Qobuz that offers much better sound quality and a lot of it in hi res, and even through the Sony and the AVR you should notice a significant improvement. Sorry to drone on, but I hope you find at least some of this useful/helpful.