I've been using a pair of ER4S at work for several years now, the whole time with inexpensive 3-Channel Go-Vibes: first a 3-Channel Classic (AD8620, AD8610), then a Go-Vibe V5 (LM6172/1), then a Go-Vibe V5 (AD8397/AD825). I've enjoyed the sound of these rigs to the point where, at home, I miss the sound of the ER4S when listening to especially well-suited music. Very recently, I bought a set of YUIN PK2 for use with the Go-Vibe V5 (AD8397/AD825). I'm finding that this set up gives me a LOT of the features of my SR225's (abundant well-formed bass, good crunch/chunk for Rock, and open, airy sound) that I really enjoy PLUS a LOT of the features of the ER4S that I really enjoy (really intimate mids and gorgeous detail in the highs). I listen to rock, showgaze, alt country, pop folk, brit pop, dream pop, trip-hop, techno, ambient, dance/trance, and some singer-songwriter: most with fronting female vocalists. With the fuller range of music that the PK2 does really well, and the degree to which (with the amplification noted above) it delivers the intimate mids and beautiful highs of the ER4S, it'll likely be awhile before I pull our the ER4S again for a good listen. But, for the several years that I used them every day, I was often in awe of what I was hearing.