I have a couple of amps and DACs in for the business and done some real world testing with them. I currently have:
SMSL SP200, Drop THX 789, and the Drop THX One version also.
DACs are the Soundblasterx G6 (using 3.5mm to RCA Kabeldirekt), Khadas Tone2, Sennheiser GSX1000 and JDS Atom AK4490 version.
The Drop THX 789 was the only one that I could connect with the GS1000x or Blasterx G6 without getting ground noise at 65% volume in either gain. Tried other cables and USB ports, you name it, the THX handled it no problem with a silent noise floor all the way up. The SMSL SP200 is a clean sound, not sterile like a Topping L30, but not as "fun" and relaxed as the Drop THX by comparison with more depth to the sound stage on both of those. The SP200 is accurate and micro details stand out much more than the Drop THX amps. The best music experience overall was the Drop THX amps with the JDS Atom DAC. For gaming it was a tie between the G6 as DAC and THX 789, but the Khadas Tone2 with 32 ohm MMX300s was super accurate for distance and direction. For music it was nicer than the original tone board I had for almost a year.
I'd recommend the SP200 as long as you don't plan to use it with a gaming DAC lined out to it, for production work the detail level is great, and that more than makes up for the not-large sound stage effect. The balanced side measures a little less well than the RCA input (someone at ASR did a comparison test, but it was a really small difference). The star of the show with the amp is the sensation of unlimited power for headroom if you equalize a lot. Warning: Cat owners be aware at idle the SP200 runs at 103 degrees F which isn't hot, but it is the ideal cat sleeping temperature... The Drop THX One is the fun one if you don't plan on balanced headphones, the THX 789 full size is if you plan on putting a gaming DAC on it. The SP200 is accurate to the point I have more songs to upgrade since the bad ones now sound like total rubbish, but the good ones sound even better
Also for the SP200 the Topping D10b is a terrific performer, but having fun with the JDS Atom DAC too, both transparent.