> You're slightly over-estimating the power of many mobile CPUs.
More than slightly. Pulseaudio's mixing/filtering stuff is using tens of percent of CPU on N900. It's more computationally expensive than the whole vorbis decoder. It's problematic (e.g. for webm playback in a browser).
> you'd pretty much be forced to work with 64-bit floating point
I'm pretty sure thats BS. Outside of some numerically unstable filtering internals there is no reason to have that much precision in any general audio pipeline.
But even 32-bit float is more or less a non-starter in some existing environments.