Upgrading from RDi SOA version 7.5

Hi all,

At our shop, we are currently using RDi SOA version 7.5. Now, I want to
upgrade to the latest version of the product. As far as I know, it is not
possible to upgrade using Installation Manager. Now, I wonder how to
proceed. What software should I download? Should I do a fresh install, in
new directories, and then uninstall the old version? What are the best
practices?

On an IBM site, I found the following three downloads:

IBM Rational Developer for System i SOA V8.5 for Rational Business
Developer V8.5 Core Multilingual Multiplatform eAssembly(CRJ07ML)
IBM Rational Developer for System i SOA V8.5 for Rational Business
Developer V8.5 Optional Multilingual Multiplatform eAssembly(CRJ08ML)
IBM Rational Developer for System i SOA V8.5 for Rational Developer for
Power V8.5 Multilingual Multiplatform eAssembly(CRJ06ML)

There is no mention of Rational Business Developer itself. Should I look
elsewhere for finding RBD? If so, where?

By the way, I am (still) confused about the naming of the products, and
how they relate to each other. In my understanding, we are currently using
a combination of Rational Business Developer (RBD) and Rational Developer
for i. This combination is known under the name RDi SOA. Is that correct?
Is it still valid under version 8.5?

I hope someone can give me some good advice, because I always feel rather
uncomfortable when starting upgrades like these...

Ewout