I managed to audition RC-1580 preamp + RB-1582 power amp and I was so well and immediately impressed that I decided to go for the new RC-1570 preamp + RB1582 MKII power amp.
After two weeks listening to ROTEL RC-1570 / RB1582 amps at home, I can say they sound natural, warm, very controlled, smooth, detailed, but not too detailed, and with this great bass. The bass is powerful, deep, articulated and well controlled. I love it. The 200 Watts make a huge difference as you feel the power driving the speakers and the music. It is also quick and has good timing (swing and forward motion) and dynamics. It makes you want to listen to music. It sounds perfect to me. Sometimes I think that it may too perfect to be true... And they look great, specially the power amp (I bought it in silver and the preamp in black, so the power amp could be the shinning star in my audio system, which is dominated by black colour).
Depending on the music you listen to and your personal audio listening tastes, you may use a less revealing (less sophisticated) speaker or more revealing (more sophisticated) speaker. As I am a bass oriented listener, a cheaper speaker with a good and generous bass response tends to be more satisfying for all kinds of music I listen to.
As I listen to intense rock music (including metal, industrial, sludge, drone, etc.) along other types of music like world music, rock-folk songwriters or exploratory electronic music, and I like the mids and highs to be laid back and not too detailed/refined/bright, I prefer having those ROTEL amps playing with my old Monitor Audio Silver RS6 than with the much better speaker that is Monitor Audio Silver RX8.
For some old metal CDs like Pantera's "Reinventing the Steel" or Crowbar's "Equilibrium" the RX8 was too detailed/open/clear/bright in the treble (mids and highs) and then it got too tiring as one's brain had to process a lot of treble information. In my personal way of perceiving sound.
The ROTEL amps paired with the RS6 give NOT a better sound in the audiophile way, but a more comfortable, warm and musical sound. It makes me listen to more music and to all my CDs, including the ones with less sound quality from the 1990's. I prefer listening to all my music collection and sacrifice some higher quality audio equipment. Music comes first. That's the goal. The bass was much better in the RX8, oh yes, but one can not have everything... You have to make your options. The overall result is the most important part.
It is amazing the difference in quality between the old Silver RS6 and the new Silver RX8, which is much more audiophile. However, for intense rock music, less speaker sound quality may be better. For me bass can be audiophile, but not mids and highs if these are too revealing (harsh, crisp, bright, prominent). I prefer downgrading the speakers than the amplification, because I like to have a powerful amp with reasonable good quality. If you downgrade here, it is difficult to find an amp with a certain kind of power.
These are my first experiences and impressions with ROTEL RC-1570 / RB1582 amps.