Embedded vcenter appliance 5.5 to 6.0

Hi

We have two sites with a vcenter appliance embedded in version 5.1 u1  with external Oracle data base (Same windows domain).

We will want upgrade to 6.0 version and we will can use linked mode.

- Oracle is ok

- The mimimal version for upgrade 5.1 u3

- The best configuratión PSC in external version.

What is the best upgrade plan?

Example:

Embedded 5.1 U1 --> Embedded 5.1 u3

   Embedded 5.1 u3 -- > Embedded 6.0

        Embedded 6.0 --> migrate to external PSC 6.0

Went two sites are with in 6 with external PSC configure linked mode.

Other options?

Thanks

Mikel