I will repost what I had written on CA forum:
ORT5 and AP are a bit difficoult to compare, as they sound very different to each other.
ORT5 is a bit dark sounding. You will not get the vast sound stage that AP1/2 will throw, you will miss some spatial clues and decay trails. On the positive side, ORT5 has the best texture out of all converters I tried, and was the only converter that fully matched my Scarlatti CD/SACD transport in that regard.
AP has superior resolution and better microdynamics than the ORT5. If you voice your system around the AP, ORT5 will most likely sound a bit muted.
That being said, in some systems AP may be too much of a good thing. Some people reported that AP sounded a bit bright in their systems. I belive this is may be computer dependent (since AP is USB powered, it relies heavily on the quality of USB power, so cards like SOtM USB with their own ultra low noise voltage regulators can help here).
Both converters can be improved by adding a decicated PSU.
A friend of mine - Marcin of JPLAY fame - who borrowed ORT5 from me, reported what he called 10% improvement in SQ by substituting the supplied switch-mode wall wart PSU with his KingRex linear PSU. Aparently, Empirical even makes their own battery PSU, called Monolitic, but it adds another $1k to the hefty price of ORT5.
AP recently introduced what they call a PurePower battery PSU. This is a $449 option for both AP1 and AP2. I recently got one, and highy recommend it. AP+PP sounds smoother, has better texture and even better soundstaging that the plain vanilla AP.
AP+PurePower can now rival the M2Tech 3-box solution sound wise, but it is cheaper, much easier to use (no manual frequency change necessary), comes in a one box less and brings much less cables.
If you already have the AP2, I think that the most sensible option would be getting the PP upgrade installed. If you want to spend more, simply sell your gear and get the new $3k Metrum HEX with the USB input module option (no converter necessary).
