Standard dhcpc should work just fine. Its nice when standards are .. 
umm.. standard.

As far as the port 25 block.. a few options are running your remote SMTP 
server on a secondary port (port 2500 is popular), setting up an SSH 
tunnel (it is an option :) or simply using Cox's SMTP servers. I have 
been using Cox SMTP servers for outgoing and haven't had problems and 
mail seems to be delivered very fast, so I'm satisfied.

If your thinking about running a mail server off your residential 
account .. It's not going to happen without using some type of a 
intermediary that accepts on port 25 and routes to a non-standard port 
on your local system (DynDNS.org appears to offer something like this). 
Cox in their acceptable usage policy states that no servers are allowed 
on a residential account. AFAIK they don't complain too much if your 
using higher numbered ports and not using excessive bandwidth.

Overall, I like Cox .. most of the time it is fantastic .. occasionally 
it has been my experience that they go down consistently for a few days 
in a row for a half hour here, 45 minutes there.. Given the time of day, 
I'm guessing it is due to local construction or network upgrades or 
something similar. Needless to say, that hasn't happen for quite a while 
(last spring?) and since them, AFAIK, its been online 24/7.

While I am not familiar with the residential Sprint broadband, I do know 
of a business that has Sprint wireless broadband (I'm guessing thats 
what your referring to) and Cox is quite a bit faster (5-7x), 
significantly lower latency and more reliable. It seems like every other 
month I receive a frantic call from that company that their Linux server 
is down (I'm their support guy) -- it always ends up being the broadband 
connection.  hehe..

Joe