I've owned the ER4 a long while, until the cable finally failed recently, anyways. Of all the speakers I've owned (including Maggie's) the ones which remind me most of the balanced (yet extended) and transparent sound of the er4's were the New England Audio Resource 50me's. A criticism of these speakers was 'dry' but I tended to hear that as balanced. I really missed them.. so much so I finally tracked a working pair for $560.. much cheaper than the first time I bought them, haha. Cost me almost as much to ship from New Hamshire to Los Angeles.
Drivers were proprietary and had no spiders, only ferrofluid to center the cone, and this made them fussy. You sometimes (once a week) had to carefully manually realign the ceramic oxide aluminum cones of the woofers w fingers to have them be perfectly centered otherwise they'd rattle a little.. but ironically not something I've had to do with my last pair.. which are about 20 years old. To this day they are my main speakers. A pair of large and sweeter sounding Von Scweikert's are in boxes, which while nice to listen to, just sounded colored to me. I could not hear upstream component changes with these or the Maggie's like I could with the NEAR's.
But am a big fan of the Ety ER4.. and NEAR 50's.. for the same reasons. You can pry them from my cold dead hands... etc etc.