Gregm & Pgleekel -
The Mephisto is good in all types of music but I have found will sound better with certain power cords and interconnects. Currently I use Audio Note AN-Vz interconnects and a NBS Statement power cord. This combo produces the most realistic sound I have heard from a player thus far. The NBS gives a weight and power to the music - intense dynamics and speed - the Audio Note seems to collapse the soundstage a little - tightens up the blur of the players - and shows you a realistic life like presentation. The combo is stunning.
When used with a Shunyata King Cobra, and Stealth PGS interconnects, I found the Mephisto to make almost any kind of music sound like something you might hear in a coffee shop. In this configuration it has a way of making blood chilling heavy metal music sound like something from Barry Manalow - I am kidding of course but if you try the combo, you'll know what I mean.
Anything in-between will adjust the Mephisto to suit your tastes.
The Audio Aero has received great accolades recently. While it is a great player - I think the number one advantage is the remote volume output. I am not a huge fan of digital preamplification so I personally do not see this feature as an advantage. A good preamp is the cornerstone of a good system. To do without is fine but - there is something lost in the musicality of it all.
The AA and the Mephisto both use the same DAC and therefore have similar character however I was not able to get to deeper levels of listening with the AA as easily as I was with the Mephisto. Perhaps the Mephisto is a bit more seductive in the way it plays.
The only annoying thing about the Mephisto is its high pitch noise it makes after you shut it off and turn it back on. This noise goes away after a while but with sensitive equipment - can be noticable for a few hours. To avoid this, always leave the Mephisto turned on.
Either way you cannot go wrong with these players however my preference leans toward the Mephisto.