Does the TiVO not have any built in authentication? (I know little about Tivos).
Regardless, there's no such thing as too much security. A reverse proxy is indeed what you require to further secure such a connection, and Apache's mod_proxy should be able to do this, but it requires a bit of setup.
http://httpd.apache.org/docs-2.0/mod/mod_proxy.html
I'm unfamiler with Oreonsp, but it seems to be very similar.