The thing about SCJA is that while it doesn't go nearly as deep into the Java API as does the SCJP exam, it is much braoder in its approach. Everything from such topics as Message Queues to Micro Devices are on the exam. Again, nothing too in depth on the Micro API, but certainly questions that I wouldn't have known the answer to if I hadn't done some extra research before jumping into the exam - and I already had my SCJP before I wrote SCJA.
But, with a good grounding in Java, the API questions will be a lead pipe cinch. But the SCJA exam is easier in some places, but it is also different in its reach as well.
Best of luck. Please check out my signature links for some mock SCJA exams, along with my relentless plugging of my SCJA Certification Guide.