Traditionally, Mazdaspeed vehicles are good indicators of the performance of the next gen vehicle. For example, the MS6 was around 270 hp and the 2g Mazda6 is around the same number.
hm. i never noticed that, but you are correct. the msp was about 160 hp, the mazda3 with the 2.3 is 156.
the msm was 170 the newest mx5 is 166
so it looks like its always a couple less than the previous generation mazdaspeed version.