With a whole-house filter, the modem should be on an isolated jack. Unless there is an issue with the existing wiring, the stats outside should be very close to what you get inside. If not, you will need to replace the cable run to the modem jack.
reply to billaustin All looks good. Speeds outside are consistent. Spoke to CL and they said I should see a slight speed increase in the next few days as they update some things in our neighborhood. We're in a rural area so I didn't expect blazing speeds anyway.