Note to start, I do not install Directv but i deal with it alot-

it will depend on what's installed now-

if you have an old 4-wire Multiswitch and 4 wires going to the LNB you can replace the LNB with a swm13 LNB which only needs 1 feed, then use a two splitter to feed the original STBs on a splitter at the original distribution point on one leg and then use the existing line over to feed another splitter to feed the new boxes at the other.

as the name implies, you are limited to 13 STB total in the system..


OR
I could be completly wrong

[Link: blog.solidsignal.com]