Hello,
The answer to your question really depends on the client, and the number of users they have at the remote site.
Number of users/phones at remote site:
5 users or less: I would suggest that you deploy one UC500 at the main site, and connect to the remote ASA though a site-to-stie VPN, with the remote phones registering back to the UC500.
6 users or more: I would suggest that you deploy two UC500's one at each site, with a site-to-site tunnel connecting the two sites together.
Thank you,
Darren