At this point, you don't need to take more practice CATs - you already know what your practice scores are and you don't actually learn much about how to get better simply from taking a test.
These tests all have a standard deviation; on the real test, it's about 30 points, and on our tests it's about 50 points.
So you do have a chance to score 550 on the real thing, but you could also fall short - your scores are right on the cusp there.
Did you take your practice tests under 100% official conditions, including essays, length of breaks, etc? If not, then your practice scores might be inflated, and that would mean you're less likely to hit 550 on the real test day.
Are you having any timing problems? Do the analysis described in the below article to find out:
http://www.manhattangmat.com/blog/index ... ice-tests/If you have timing problems, then that increases the likelihood of problems on test day that can lead to a score drop.
So the important thing is to figure out (a) how valid your current data is, and (b) whether you want to go in and take a chance and hope you will get that 550 on test day next week (but you might not), or whether you want to wait a bit longer until you have fixed any timing problems and your practice scores are a bit higher than your desired score on the real test. (Ideally, at this level, it'd be nice for practice score to be 30 to 50 points higher than your goal score.)