i test all sorts of systems-
i have just spent several weeks looking at photojpeg performance-
the graphs here are using an esperance 2GB RAM disk- which give me the absolute maximum possible performance- because 'disc' speed is almost infinite.
you cant get any faster than this - right now - whatever RAID you use.
these tests are for 4 layers - on 8core intel and quad g5.
and for 2 layers - with 2 layers its possible to do almost anything-
this is a graph of 84 photojpeg files - in 5% steps from 35% to 100% - and from size 640x480 to 1920x1080.
these graphs show the raw cpu time necessary to do these things.
the axis are codec and time in milliseconds.
the clumping of points around 40ms is when testing has broken down and tests are not valid.
intel 3.0ghz is faster than quad g5 at most data points - but not all.