You can buy a new one or add it - either way doing a 301 from the old domain to the new domain is the way you want to go. Will you still own the domain and its just a case of copyright?
Subdomains allow you to actually have additional site, filter down a lot of the
PR and authority down to the subdomains. You can also hist the subdomains on other servers, such as a server in the target country.
Lastly, you can go into Webmaster Central and designate the site as targeting that same region/country and get a little boost in your rankings and traffic.
So the final search results could have both of your websites ranking side-by-side in the top 10 results like you see below;
