I passed SCBCD and then SCEA (part 1).
And it's true that SCBCD really helps in topics such as Security, Transactions, Scalability, Messaging, etc.
In SCEA, there is a big part of
EJB and related
patterns.
So, SCBCD is not required but it helps a lot.
But I recommend you to pass directly SCEA: preparing yourself for SCBCD will oblige you to go deep in the details of EJB development (that is out of the scope of SCEA) and will be costly (200$).