Capacity for UnDP pollers

We have a couple of Orion servers which have met capacity regarding element count. We need monitoring of websites configured on our F5's and so we need to understand the limitations of Orion as it pertains to capacity of UnDP's per Orion Polling Engine. The long term plan is that we will be monitoring approximately 10,000 websites and approximately 6 UnDP pollers per website for a total of 60,000 UnDP pollers assigned. Can you tell me where we will start to see capacity problems and when we need to balance to a secondary server?

Thank you,
Jason Henson
Loop1 Systems