I think it's residency and specialty dependent, b/c I know a lot of ortho guys in my class who were taking step II CK in March.
As far as anesthesiology, I would check with the residency. I think many need it as a requirement before starting residency. Some programs may need passing Step II CK as a prereq for them putting you on their match list, which is finalized like Feb 21 or something. It's the same date as the final day you have to submit your ranked list. Again, check with the residency if possible. I know you probably have like close to 30, and it isn't feasible, but I don't know what else to say. I wondered this myself when I was in going through it.
Also, Step II CK takes about 4 weeks to come back. It's pretty much 4 weeks on the nose. Step II CS takes about 8 weeks to come back. I don't think residency programs give two flips about CS, just as long as you pass sometime before you start. Just be aware that you have to schedule CS like 3-4 months in advance, and then you don't get your score until 2 months after you take it. It's like 6 months from the time you sign up until the time you get your score, and you probably study 1-2 days. I was anal and studied 5 days. You gotta make sure you pass that thing, b/c then you're looking at another six months before you find out if you passed a second time. OH, these six months are considering you don't wait to get a date that "becomes available" online. Meaning someone cancels and you take their date, which is like a week from the current day. First Aid Step II CS was great for the test. Anyway...