I had an amnio, because the CVS was new at the time and they were still having problems.  I would, if I had to do it again, have the CVS. I felt the DEX effects got worse overtime.  I did not have the results from our amnio back until 22 weeks.  We have two SW CAH boys,  both doing great, 6 and 9 years old.

Good luck to you, it is all worth it in the end.