Which domain name should I choose?

I'm making a website, and I need to choose a name and URL for it. Right now, it's only going to be a blog about my life, but eventually I'd like to expand it to include articles about environmental and social issues, as well as life advice. My nicknames are Kay and K9, so I was thi9nking either Planet Kay, Kay's World, Planet K9 or K9's World. The domain endings I like are .ca (I'm from Canada) and .org (not sure whether it's appropriate for the sort of site I want). Which of these do you like the best?

www.planetkay.ca
www.planetk9.ca
www.kaysworld.ca
www.k9sworld.ca

Thoughts? :)
I agree, I like www.planetkay.ca and www.kaysworld.ca. I'm leaning toward the first one, because it rhymes and is sort of catchy.

Hi from my opinion "www.k9sworld.ca" is the best domain name for your website ..If you to like the same then first check that whether it is available to register or not ..If it is available then register it through online vendors like 9cuebhosting.com for affordable cost ...