You can't.
But maybe I don't get you request:
This is where I'm having some trouble. I want all blogs under this previous subdomain to just point to thekartel.com/news/pop-rox-nation.html
So, I would like to understand the problem.
Now you have a Joomla site (with ReDJ) under thekartel.com, and from the CPanel you configure a lot of third level subdomains, and all of these are "served" by this Joomla site. And you would like to manage them as they are different requests from different sites (one Joomla, many sites).
Is this correct?
Luigi