Don Sachs used to upgrade/modify Macintosh and HK Citation gear until he ran across some gear designed by Roy Mottram. Some was to upgrade Dynaco amps, and he also had a beautiful sounding preamp of his own design. Don found that he could apply many of the modifications that he had been using on Macintosh and HK tube gear for decades, and Roy’s improved upon designs sounded better than the Macintosh or Citation gear. In addition to cleaning up the DC which improves the "sound floor", he discovered some amazing toroidal transformers that leave practically no fingerprint upon the sound. Roy also designed his own preamp, which Don’s modifications make it another amazing value. Don is semi-retired, and his gear virtually never shows up on the used market, so you may want to talk to Don sooner rather than later is the way to go. Generally I like to follow the GIGO rule, garbage in garbage out rule which would have you start with a DAC, and then progress through your entire system. Until you have great source material you’ll never fully appreciate your electronics, and until you have great source and electronics, you can never appreciate your speakers, etc. In this case though, the DACs and speakers will be there, Don could decide to go into full retirement at any given time, so time isn’t your friend. One of the big pluses with Roy’s better mods, which Don Sachs takes to their full potential, are the 6SN7 tubes in the preamp and amplifier. I’ve had modified/improved preamps like the ARS LS-15 Prep and as nice as it sounds with good 6DJ8 BugleBoys and good capacitors in the audio path, the DS2 just spanks the LS-15, which you would likely love, until you heard a DS2. I have one of Roy’s custom amps and I am applying many of Don’s modifications to it, but what I didn’t know going in is how much money I would have saved had I just purchased Don’s amplifier... For now my ML 27.5 is doing a respectable job though. You can certainly speak to Don about any protective circuitry that you may want.