I might be misunderstanding, but it sounds like this can be accomplished pretty easily using just the Views module (The RSS display module might be separate, not sure).
Example:
On your content type you add a mulitselect field for clientA, clientB, etc
In your view, create an RSS feed that shows that content type. Name it 'feed for client A'. Then in the filter, choose only nodes that have that client selected in the multiselect field.
Then you just pass the the link to the RSS feed off to the client.
If this is more complicated and you need something more dynamic kindly disregard.
Hope it helps,
Patrick