steffen, maybe my statement it would be *worth thinking about* has been drowned out by the amount of involved details ...
direct from disk is also called (patented?) the technology from NI which also cannot cut out buffers for sample headers .. such a *read ahead* technology is a totally other approach to sample based arrangement - we could do a lot of midi detection and processing during such 300 ms which would finally result in a kind of *sample rendering* engine and might also be worth to think about it.
the neccessary latency for the MIR is caused by the nature of convolving and i'd say there is nothing to be sacrificed ... compare with CGI (Computer Generated Images) ... to draw a simple shadow works easily realtime, to show even the first reflections (from objects within a scene) works too, but to render a realistic movie containing several layers, a dozend light sources and reflections (meaning the depth of reflecting light on surfaces, not the number of reflections) is impossible realtime - you would either need incredible CPU power and a high delay or accept offline rendering.
AFAIK convolving in sequoia adds at least 1024 or even 2048 to the latency, and the impulses are not very much and long in this case ....
christian
and remember: only a CRAY can run an endless loop in just three seconds.