"Merrick " you've probably noticed by now is already on the site. Too bad those blue hotlinks don't crop up *before* we post! LOL! :)
"Sirius" comes from the Greek and means "sparkling" or "sorching". This name for the Dog Star first appeared in the writings of Hesiod, but it has also been applied as another name for the sun.
I think that both "Sasha " and "Sacha " stand on their own quite well as independent names. "Sasha " has been a Yiddish equivalent of the name "Alexandra " for generations, in fact.