Which is best for a pen-name?

Question:

Which is best for a pen-name?

I'm thinking of these. I want them to be cool but not awkward. And the first name and surname (last name) should go together when spoken out loud.

Elijah Black
Caspian North
Sydney Blake
Edmond Blake
Cat Martin (or Martyn if you prefer)

Choose one of the above please, tell me "what feeling" each name gives you (why you like it?) then if you wish, suggest one of your own. I'm asking this again for the last time.

Best Answer - Chosen by Asker: Wow, I stink at finding names that go together, and these all do! Kudos for that. However, my opinions on each are as follows.

-Elijah Black: this sounds more like a character than a writer. I find myself envisioning a person who goes with the name, and I don't think that that's what a pen name should be for. I think that Elijah Blake would sound much better.
-Caspian North: a bit more like a place than a name. Like, there's the Caspian sea, and North is a direction...Not the one I would pick.
-Sydney Blake: I like this one! It sounds like a writer, and it's nice and gender-less. Basically, it would give you a nice anonymity.
-Edmond Blake: This one is really nice too. It's elegant, but still rather anonymous- the kind of name the benefactor would have in some gothic novel.
-Cat Martin (or Martyn if you prefer): Rather contrived. Maybe this would work with a sci fi writer, but for anything else it just sounds like an anagram.

In sum, my favs are Sydney and Edmond Blake, and my least favorite would by Cat Martin. Good luck with your pen-name using! I hope I helped.

EDIT: I like tngapch's suggestion! Initials are always fun.