well, based on latest article on the domain guru kevin ham, he paid $75k for a domain, greeting.com (i think) and some domains go for $XXXk, so its really relative how BIG a FISH you are in the ocean
Close your eyes and go for the .com. It would be 10 times better than .com not for the search engines but for your visitors. Everyone knows .com. Not many know .org. You will definitely have more repeat visitors. Also, you would be getting a aged domain which would further the seo. Good luck. Stan.
Think about how much cash the site is going to make. If you can make more than $2000 then buy the domain name. There aren't many sites running on keyword.com these days.