I still have my Stax SRM T1 amp energizer, from back in 1988:
View attachment 91581
This was considered over the top in cost at the time. I also had the Stax Lambda Professional headphones:
View attachment 91582
To be honest, these were the best tools for my purposes at the time. The biggest flaw was the cord for the headphone. I take that back, the biggest flaw was my severe case of audiophilius nervosa: I made a fixed resistor bypass for the potentiometer, replaced all passive components [resistors, caps, wire] with "high-end" substitutes. Managed to destroy a JFET in the process. Fortunately there was a nearby audio repair shop that could fix it, being as this was Berkeley in the nineties and there was quite the audiophile scene in the town at the time. I managed to wear out/destroy two Lambda type 'earspeakers', and by the time that all happened, I was out of the business of recording other musicians anyway.
If I was in the same situation today, I would use what I've got now. I wouldn't have been aware of this bit of kit unless I read ASR. I've got Drop 6XX headphones and the mini-stack of Topping E/L 30, hooked up to an Acer Aspire 5, which appears to be the cheapest decent Windows laptop right now [$364.00]. Mostly I'm listening to Apple Lossless files from a flashdrive that holds half a terabyte. Some of the files are MP3 of different data rates, some are uncompressed Redbook. Otherwise it's whatever's streaming, YouTube, Tidal, various sources for TV.
Clearly it's a different world now than when I first got the Stax amp & 'phones. They probably were the most refined and detailed sounding transducers I've encountered, but they also had plenty of problems, many of which are addressed by the Drop-Topping combo. First, the cord connecting the earspeakers to the energizer amp was just a little bit too long and difficult to replace. Alas, I had the wheels of my desk chair run over that cord once too often (twice!). Also, expensive to replace the cord, and not easy to replace. The Drop 'phones use a cord that's easy to replace, not too long and not expensive. There might have been more detail and nuance in the earspeakers, but that also could be due to elevated treble as the sound could get harsh. Bass was clear and clean, too bad there never was quite enough of it. The Drop 6xx's are similarly light in the deep bass [also overcooked for the next three octaves, an issue the Stax did not have], but there's the APO EQ to iron that out, and that treatment really works, as Solderdude notes elsewhere. If the Drop headphones seem to have a little less treble detail, that might be on account of my encroaching deafness. No question that the Topping amp and Drop headphones can play a lot louder, though that's not really an advantage for me.
These reviews [Warning: contains subjective content] align with my memories for the most part.
https://www.kenrockwell.com/audio/stax/srm-t1.htm
https://www.kenrockwell.com/audio/stax/sr-lambda-pro.htm
If a pair of Lambda 'phones were to drop into my lap, I'd drag out the SRM T1 out of storage, but that's about it for me. It's just one more thing in my rear-view mirror.