Not sure I understand your question, so will try to elaborate:

all the timings were performed on n900 with CPU locked @ 500MHz by using the test program. We still don't have all the pieces together, so running xprot "in action" is still not possible. Despite that, I expect to see lower CPU usage with replacement, as the above timings are on the algorithm that does the job. i.e. faster processing == lower CPU usage.