Of all the keyboards I've owned and tried, the PSR9000 is the "most country" out of the box. It has all the lead sounds, and most of the styles.
Of course any of the keyboards can be taught to play country. Most of them are good at the newer stuff, but the older basic styles are what's usually missing. Fortunately they are easy to make, if you can't find them on the internet somewhere.
I don't see how you can really go wrong with any of the modern crop of keyboards. Some just suit different people better than others.
DonM