Here is a suggestion:
Keep one landline.
Cancel the other.
Sign up (if in in the US) for something like Phone.com (I personally like them)
Get a dual phone (one landline+one VOIP line) like the
S675IP
Set it up.
Enjoy life and read wise books.
P.S. 300 meters is a fairly unreasonable requirement for a consumer phone (unless you live over a body of water.) If you get 200 feet, you should be happy....