The ER6 are definitely edgy in the highs (with about 20% of my CD's, the edge to the highs takes me out of my comfort zone, but not quite into actual harshness). From Scrypt's comparison of the ER6 to the ER6i, the 6i seems to NOT have the hump in the highs that gives them that edginess. The ER6 are also fairly light in the mid-bass to bass region (my main cans are the AKG K501, so I am NOT a bass-seeking listener). To say that the ER6i has more bass says to me that they are more balanced than the ER6. Given the limits I hear in the ER6, and from the descriptions that Scrypt and others have given of the ER6i, it seems to me that the ER6i would be the more balanced of the two (ER6i, ER6). The ER6 are somewhat colored toward the highs. It takes some equalization for me to fully enjoy my ER6 (to lower the treble hump and to bring up the bass to mid-bass region). And this is with a Go-Vibe fitted with either OPA627's or a OPA2227, both of which are darker than the AD8620 in your Go-Vibe.