Hi Mohammed,
The UC540/560 supports 8961, 9951 and 9971. But these phones are very limited in functionality when used with UC500 as they are SIP phones and UC500 does not have good support for SIP phone features as of now.
You can do point to point video on these phones, however here are some restrictions
- No Teleworker support
-No Multisite support
This means that you can do point to point video only inside the same network which is not useful in most cases. If you want video I would consider the BE3K and 6K. 3K is a new product and is limited in funcationly currently. However does full video with 89xx phones. 6K is fully featuered.