LM4562
Everyone who's heard a LD MK1 knows the sound. It's very accurate and has pretty good extension on both ends. It leans towards bright and the mid-bass is a bit on the lacking side. It does a good job presenting piano; though in the lower ends it lacks some body and depth. Also it lacks a visceral feel when presenting a bass riff for rock music. For voice, it feels intimate but slightly veiled... like you're listening on the side of the stage kinda. The bass impact is there on the low end and the extension doesn't clip off on De La Soul - It's like that. I usually lose a little off the bottom end on that song. It still is a bit rough though the whole bass end, but not enough to detract from anything.

LT1469
The LT1469 is very fatiguing on the high end. The veil has been lifted, but it is very bright IMO. The shimmer on the cymbals and high hats is too much. This would not pair well with a grado, but maybe it would be good for countering a particularly dark headphone. If you're listening to a song that is pretty mid range intensive, it sounds really nice; but if you pick up some female vocals or any sort of music with drums, it gets fatiguing too fast. Ideally, this is nice for colorizing male voices or some classical music. Maybe acoustic, but definitely not blues, jazz, or hip hop. The vocals are again intimate and I already said earlier the veil is lifted. Male vocals sound nice on this for sure. Bottom end has little impact and the extension isn't as nice and rolls off fairly early. Listening to a log sweep... jeez, once you hit the mids, the decibels really go up. It is pretty glaring that these have major bass roll off.

OPA2111
The OPA2111 has the bass that the LM4562 and LT1469 are lacking. The spatial presentation is much better compared to the previous two; it's less intimate, but more spatially accurate IMO. This opamp pretty much played nice with anything I threw at it. On the log sweep, I heard a bump in decibels starting just in the midbass region and just before high mids, then there's a slight recession in the highs but it picks back up. I think this a pretty good all around opamp. It's a little bright, but just enough for some treble sparkle. It's a little bass heavy, but only in a range that presents rock/blues well. The bass thump needed for hip hop music isn't as strong as I would like, but it sounds nice. Um... as for vocals, piano, blah blah blah... everything just sounds nice on this how else can I describe it? hahaha

LT1364
The bread and butter for the MK1 according to the other thread. Where do I start with this one? So the mids and highs are really nice on this. Guitar riffs sound awesome. Bass lines aren't as nice the OPA2111, it lacks the visceral feel. The voice presentation is a little more veiled compared to the OPA2111, but it is much more open compared to the LM4562. The treble is much less bright but it isn't dark, it feels fairly neutral. This is probably the cause of the less open feel. The mids are very strong (which is why guitar riffs sound so awesome). Listening to the log sweep, the bass extension is the best but it lacks that midbass hump which helps the OPA2111 with its bass performance. The mids have a jump in decibels compared to the other opamps also. This also sounds great with everything, but in a different way.

Conclusions:
OPA2111 and LT1364 are the best of this batch. Looking below, every > symbol represents a noticeable degree difference in comparison between the two units. So if there is ">>" then it is two times more noticeable that it is better.

bass OPA2111 > LT1364 > LM4562 >>>> LT1469
mid LT1364 > OPA2111 >> LM4562 >> LT1469
high LT1364 = OPA2111 > LM4562 > LT1469
male voice presentation LT1469 > LT1364 > OPA2111 > LM4562
female voice presentation LT1364 > OPA2111 >> LM4562 >>>> LT1469
classical presentation LT1364 = OPA2111 >> LM4562 >>> LT1469
guitar presentation LT1364 >> OPA2111 >> LM4562 >> LT 1469
bass guitar presentation OPA2111 >> LT1365 >> LM4562 >>>> LT1469
acoustic presentation LT1365 > OPA2111 >> LM4562 >>> LT1462