more depends on the network than on qlikview. The users from the new site will have to be able to "see" your server, that is be able to see through your firewall into the the domain in which your server is sitting. If you are using NT authentification there will need to be a trusted domain setup.
the plugin is (very) sensitive to network glitches so bandwidth is important. But given that you only have two (big) sites to be connected I'm sure the network people will be putting together a decent package.
Basically I'd leave the qv server(s) where they are, make sure there is good network connectivity, the domains are trusted, the new users can see the sarvers ( most of this goes hand in hand).
You can do this with the help of custering.
For more information on clustering, visit below links.
Hope this will help you