seems good, per below doc the above licenses should support 800 calls as per your requirement, contact licensing@cisco for installtion assistance and requirement.
• Pay-as-You-Grow (or session count) license—This type of license covers the right to use the feature as well as the maximum session count allowed. An example is the FL-CUBE-25 license, which allows up to 25 sessions. This license is designed to allow a specific number of sessions (or calls) on a platform. Purchase only as many sessions as are required in your deployment. You can add more licenses later as your needs expand, thus offering pay-as-you-grow benefits.Session licenses are stackable. These licenses are available on select platforms as shown in Table 1 in the section CUBE Licenses, and are available on all software images. Examples include the FL-CUBE-4 and FL-CUBEE-100 licenses.
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube/configuration/cube-book/voi-cube-licensing.pdf
Regards,
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