I've got my Asterisk box Setup with a Granstream FXO to connecto to the Land Lines.
I've got a FXS to connect the Analog Phones to Asterisk also.
Now, when I call from the Analog phones call quality is great, but when I call from a Softphone (Zoiper), call quality sucks. I've tried matching the Codecs (FXO has GSM as primary Codec) with no luck.