This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
If the *only* reason that you want to upgrade to the OCP Java 7 Programmer certification is that you want to write the 'Professional' Java exams, then you don't have to. With the SCJP6 certification under you belt, you can write all the other Java exams, which have OCP Java SE 7 Programmer exam as their pre-requisite.
For an example, the Oracle's information page for OCP Java EE 5 Business Component Developer certification states its pre-requisite as Oracle Certified Professional, Java (SE 5, SE 6,or SE 7) Programmer OR Sun Certified Java Programmer (any edition).
Is there any other reason, why you wish to write the OCA Java SE 7 Programmer exam?