What was your major? If you were in a technical major and you want your certificate to enhance your technical career, you must go for SCJP. If you want to go into management and related fields, not technical, then having SCJA will show that you know enough Java to deal with it non-technically.
There is no requirement to have your SCJA for any other exam. But it's a great cert to have, and pehaps a bit less studying is required compared to SCJP. Why not take them both. SCJA will certainly expand your knowledge of the Java Platform and help you pass the SCJP exam when the time comes!