webMethods8 upgrade

We are planning to upgrade our wm 6.5.3 environment to wm8. One of the major point of concern I have is around capacity planning and hardware sizing.

I am not too sure if I can use the same hardware and same set of boxes for my integration servers & broker as I am using with wm 6.5.3. If I can I would only need to worry about the upgrading of wm components

However How much it is required to review my existing hardware and is there any tools to do this analysis? (I know about gear capacity planning and sizing spreadsheet but that talks about wm6)

Please share your experience and data about wm 8 upgrade.

Is there no one who has any suggestion on this thread?