TLDR...
So...
Received my Schiit Lyr 3 & Bifrost 2 yesterday. Using AudioQuest Interconnects and Power. Was previously using the Vali 2+ & Modi Multibit as well as a Ragnorak 2. I owned a Lyr 3 w/ Multibit card prior. Went back to the Lyr 3 after the Vali and Ragnorak. I'm in the process of building a home so I'm stuck in limbo for the next several months so I have nothing to tinker with but desktop set ups. I owned the Ragnorak 2 and Modi Multibit with Martin Logans that I sold when I placed myself in purgatory while my house is being built 9 hours away.
I've been alternating between my Sennheiser HD 660S and the RS1x. In this regard, it's not even close. A few caveats...
1. Have you ever owned Grados? If you like Grados the RS1x are clearly superior to anything in the SR, GH, HF or RS lines that I have auditioned/owned. From an aesthetic/functionality perspective they are vastly improved as well. I love the 3 wood cups and the cable is non microphonic and does not kink/twist the way the older cable did. Yes, I would love a detachable cable; but this is a nice compromise as with the HF-3. The L pads are the L pads. No new news here.
2. Never owned Grados? Do you listen to classic rock, hard rock, heavy metal, the Dead or singer/songwriter music? How is your high frequency hearing? When was the last time you had your hearing tested? Ever listen to Klipsch, Bowers & Wilkins or Paradigm speakers? Grados have an aggressive tilt with a faster rhythmic pace and are more detailed on the top end. I would argue "fatiguing" to the end of my days. If you like these types of genres and/or have enjoyed these brands of speakers they RS1x will be well received. You may need a pair of G pads for comfort if unaccustomed to the utilitarian nature of Grado and their pad choices. I have used these with the L pads exclusively the past 48 hours to baseline the sound. I have found the differences with pad swapping subtle but noticeable all the same with prior Grados. In summary, if you love your Sennheisers, HIFIMANs, Audeze, etc., then buy an SR80x or SR325x as a a change of pace headphone and venture no further.
3. The RS1x scale fairly well. I can tell the improvement moving from a $400 set up to a $1,300 set up more so than with the HD 660S ironically. I had an iFi Zen DAC V2 for a minute while I was moving. I sold the iFi prior to owning the RS1x but found it a competent performer. Simply put, if I had a "tight" (everything is relative) budget I would go with the ~ $190 iFi and the RS1x vs. the Lyr 3/Bifrost 2 and a more modest pair of Grados. I would upgrade the front end as funds allowed with modest expectations.
4. As all things with the pandemic, supply chain disruptions are inevitable. If interested, I would pounce now. Grado seems to be keeping up well with production more so than other vendors, but we shall see. With other products, it has been more of a "here today, gone tomorrow" vs. a slow decay.
5. I have never auditioned/owned a GS or PS series headphone. If I win the lottery, I will let you know. My current set up is my end game for now and I am completely content with the price/performance ratio of my purchases. I may punt the HD 660S for a Sundara or Focal as a compliment and purchase a few tubes for the Lyr 3. Otherwise, I'm good.
...highly recommended. If you haven't tried a pair Grado headphones, get an iFi or entry level Schiit DAC/Amp and a pair of Grados that you can afford and have fun. Enjoy.