Speakers!!!
If you don't mind looking through resale shops, eBay, craigslist, garage sales etc with little trouble you can find many American and especially British speakers from the 70s and 80s that are still detailed but have a nice mellow quality to them.
There are modern speakers that are less analytical than the average speaker but quite often the designer went overboard IMO and the speaker ends up with an unpleasant muffled sound, like there is cotton in your ears. And it's not uncommon for the bass to also receive the "politeness" treatment - not good for rock/pop music!
If all recordings were done well, using top of the line gear and thoughful EQ/compression/etc choices, owning highly analytical speakers would be fine (studio monitors come to mind). But all recordings are
not done this way - this especially applies to rock and pop music - despite the availability of the high-resoluton formats (sacd & dvd-audio) and all the many incremental improvements in digital recording technology the past decade.
This is why many speakers touted as "super accurate", "revealing" and having "great specs" don't do much for me: all they end up doing is showing me where the bad audio decisions were made, lessening my enjoyment of the music. Many speakers thought of as particularly suited for HT use are like this which is fine for producing ultra-clear dialog & artificial sound effects and being able to launch these elements across the room into the audience's ears with little deterioration. But for
music IMO quite often this can become irritating pretty quickly.....and even for certain movies that have bombastic soundtracks that are constantly "on".
But if you listen to mainly to classical and jazz, which are usually much better recorded, revealing speakers are a better choice for some people.
My own speakers are made by Boston Acoustics which for me have a nice combination of warmth and detail. I also own some Infinitys which is my personal limit for being analytical. OTOH I have also owned Advents which are definitely on the (good) warm side. Advents sounded this way all the way up to their "death" in 1995 when Recoton Inc. bought them and Acoustic Research and ran that formerly-respected 25 year old brand into the ground by slapping their name on all kinds of crappy plastic products.
For mellow American speakers, you might want to check out this forum:
The Classic Speaker Pages FYI: this is where the phrase "east coast sound" originated. Older JBL, Cerwin-Vega, etc are of the "west coast" sound with their punchy bass and forward highs.
While highly sought after, the AR brand is probably one to be a bit wary of since many of them have 4 ohm impedance ratings and smaller modern receivers will most probably have problems supplying them with enough current. Plus - and this just my opinion - ARs can be
too warm and can cause energetic music to kind of just........lay there. Their bass output is awesome though but you HAVE to use a powerful amp to allow this to happen. While like Advent they use an acoustic suspension woofer system, in comparison ARs are major power sponges - powerful AND deep bass doesn't come cheap (Advents also had deep bass, but couldn't get as loud).
I'm not nearly as familiar with the older British speakers that share this quality but KEF, Wharfedale and Tannoy do come to mind and I think Spendor. IIRC Celestion and B&W were the more revealing of the older warm British models. Doing a search on audioasylum.com should help a lot with this.