I have two separate systems. My living room system in that YouTube video is for both TV and music listening. When I'm listening to stereo music I switch the receiver to Stereo mode so it doesn't use Dolby ProLogic decoding which alters the sound as it routes content to the other speakers. My upstairs system is a home recording studio, and that's a very different setup. This video isn't nearly as detailed as my HT video, but it shows the room and speakers:Ethan's Studio Tour (2.7 MB WMV file)
My studio speakers are large old-school JBL 4430s with 15-inch woofers and "bi-radial" horn tweeters that have an excellent off-axis response. They're bi-amped using a pair of Crown stereo power amplifiers with just over 1 KW of power between them.
Years ago I had a very nice, and fairly expensive, Yamaha stereo receiver. I think I paid $700 for it, which was a lot of money when I bought it about 25 years ago. Eventually it broke and a repair would have cost more than it was worth. So I went to Costco and bought my first Pioneer receiver. I wanted only stereo, not 5.1, but they had only surround receivers so I paid $180 and I was very satisfied. That was fortuitous because only a little later I set up my first HT system. But after a few years one of the digital inputs failed, so I went back to Costco and this time they had a better Pioneer model (more surround decoders including DTS) and it cost only $150. So I bought it and that's what I still have now. So yeah, I did buy based on what a discount store had available, rather than spending hours comparing features.
Now, speakers are a very different issue! I knew that whatever electronics (receiver) I got it would be fine. And if it wasn't I'd just return it and get something else. But speakers really do sound different, and some are definitely better than others. I chose the JBLs in my home studio (around 1990) based on my experience with them in professional recording studios. I knew they were excellent so I just ordered them and had them delivered. Likewise for the Mackie HR624 speakers in my HT. Four of my friends have the larger HR824s so I already knew they were excellent with a flat response and very low distortion. So again I just ordered them and knew I'd be satisfied.
I do have two external DACs, but not for the same reason most people get them. When I bought my current PC four years ago it has the newer short card slots, and my old multi-channel sound card no longer fit. So I gave that away and bought a USB sound card to use for recording. If I needed only playback, not recording, I'd probably just use the sound card on my computer's motherboard. Likewise for the sound card built into my older Dell laptop in the living room HT. It sounds perfectly fine, but I use that laptop for both recording and room measuring, and also for mixing 5.1 music. So I needed a pro-quality multi-channel sound card. If I didn't need that I'd just use the built-in sound card for stereo playback.