How big is the salary difference between the new job offer and your salary on the PERM? ( I believe you will get a raise :) )
According to the Aytes memo, the IO should not reject your AC21 only because of the significant discrepancy between salary of old/new jobs, but he could use it to determine that you are not doing a "same or similar" job.
This is only my personal understanding, I am looking forward to hear other people's opinion and experience.