Here are my impression over a few opamps in the E12DIY. I stuck to BUF637 this time and will look into LME49600 some other time.
AD8620 - good detail, almost edgy, a little flat on soundstage and lean on lower end texture
MUSES01 - near perfect balance. ultra smooth and full sounding with lots of texture
MUSES02 - Better depth than muses01, more layback with a little less texture
MUSES8820 - similar to MUSES01, but scaled down and not nearly as grand
MUSES8920 - similar to MUSES02, but similarly scaled down like 8820
LME49720HA - very clean and clear with good air and soundstage
OPA2107 - a little mid centric, nothing remarkable
LM4562 - similar to LME49720, even cleaner and leaner, very O2 like.
OPA2209 - a little veil on the mid and lacking detail
AD8066 - great micro-detail and decent soundstage, but otherwise unremarkable
AD797 x2 - neutral but edgy, like AD8620 with better depth
OPA1611 x2 - laidback, if not a little dark
OPA604 x2 - almost like opa1611, rather smooth.
So far none of the stock opamp really wow me. Beside MUSES01/02 which I have expected to be pretty good sounding, the only other opamps that really surprised me are the LME49720HA / LM4562 (*they are said to be the same internally), LM4562 in particular is very transparent and clean, giving a similar presentation as O2. It will serve as a great choice for those who are looking for wire-with-gain / colorless style of amplification. MUSES01 and 02 more or less about the same level. 01 has the advantage of having a great balance between detail and texture, while 02 has the advantage of having better layer and soundstage. I'll say 01 is a bit more musical while 02 is a bit more neutral in comparison to each others. Though by themselves, I won't say any one of them is really on the musical or neutral side. They are all fairly well balanced. The opomp I really won't recommend are OPA2209 (or OPA209) and OPA2107. The rest are just unremarkable one way or another.
