With your wireless broadband can it be run through a USB? (Not sure what you run in the US)
Over here I have a 3G USB modem which I plug directly into a Billion Wireless 4 port GB Router. That in turn is connected directly into the external network for the core.
Also as an alternative to freeNAS have a quick look at unRAID. I find it is very good for media storage although I have read (never tried it) that mythTV doesn't like recording to rieserFS. I'm getting a HDHomeRun and planning on recording TV directly to the core as I don't keep my recordings.