I owned the Emm Labs DS-EQ1 with the Grand Master cartridge for over a year, before first upgrading to DS GM Equalizer, and then more recently upgrading to the DS GM EX cartridge. I’ve never heard the W3 BTW.
Prior to purchasing the DS-EQ1, had an in home demo of the DS-EQ1 and the DS Audio Master 1 equalizers at the same time and I much preferred the DS-EQ1. More detail and more natural at the same time. The Master 1 sounded constrained and a bit veiled by comparison. Yes the GM equalizer is a nice step up from the DS-EQ1, but EQ1-to-GM-equalizer is well along the law of diminishing returns curve. The DS-EQ1 is fantastic - and even underpriced for its performance - IMHO.
The DS-EQ 1 works with any DS audio cartridge. The Meitner DS-EQ2 is the lower priced version and an amazing performer at its price. I would echo the above comments. I have had the Grand Master and EQ1 for 3 years and love it. I have compared to different DS equalizers and with the exception of the Grand Master two box, have preferred the Emm labs. But its just my opinion, and I like the Emm sound - I have a lot of their other gear. The two box Grand Master has superior bass - oomph, but not a lot over the EQ1 in the rest of the range. Both brands are excellent, just my preference. Hope that helps.
Does anybody know what actually goes on in the box of these decoders? How does the EMM decoder differ from the DS Audio decoder? What are they doing differently?