You can put your GPS antenna in the same location as the OEM antenna. See info about OEM GPS antenna in 2nd half of this post
(#11 in my 'Subaru stock HU info' thread).
For satellite radio, you may be able to swap your OEM rooftop antenna for the OEM version that has both AM/FM and sat. You'll probably need to run a new antenna cable above the headliner (it's very unlikely the cable for that type of antenna is pre-installed).
Note that you will
have a pre-installed sat radio antenna cable, but that ends either inside an A-pillar or above the map light cluster (to ease installation of the OEM antenna, which they place inside the windshield on the passenger side).