OK, well then compared to the SR-71, the GV5 is less rolled off in the highest highs. The SR-71 plays high notes really beautifully, but I find that it takes a some of the punch and impact out of the "sharp corners" of percussive sounds. The sound of a slap on a hand drum, say, just doesn't have the sharp attack that I expect, and I found myself compensating for it with more volume, which isn't good.
With the GV5 that attack is very present and has much more of the clarity that I get from my Gilmore Lite desktop amp. The mids on the GV5 perhaps have a little less body than on the SR-71, but if so (and I'm not truly sure), it's not enough to bother me.
I respect both amps very much, but the SR-71 gives me a little bit less of what I'm looking for when paired with the ER-4S, and I now use the GV5 pretty much exclusively as my portable amp.