The power steering doesn't use a whole lot of power, and most of the time, you're not going to be using the winch hard and turning at the same time so I don't think you'll have any problems with just the 1 stock battery. I have a 6000lb winch, and used the stock battery for almost 2 years before I upgraded to a dual battery system.
Biggest reasons to get a dual battery setup, are running a *big* winch, running the winch really hard (like stuck in mud up to the seats), or running alot of extra stuff, like radios light bars and big sound system etc, and/or wanting to use the radio/sound system while the machine is off. So it uses up the power from the 2nd battery, but leaves you with the main battery to still be able to start it.
Being in NC, I don't think you're going to use it to plow snow, are you? Running the winch constantly up and down for a snowplow is also usefull to have a 2nd battery.
But like Trigger said, use a nice big fat cable from the battery back to the winch solenoid, and tap off that for the power steering.