Gnarls sounds like snarls like the sound of a mad dog or a mountain lion, not like a name.
Simeon conjurs up images like This and This
Xavier sounds fine, but it would a little odd if the child wasn’t at least part Hispanic or Latino (like if he was a blonde haired blue eyed nordic looking child, or an Asian child) One of the coolest boys in my junior high, however, was an African American kid named Xavier, but everybody called him “X.” So if he’s not Hispanic or Latino, but he’s cool then it might work. On the other hand, one of my nerdiest school chums was a blonde, super-white kid, almost bordering on being an albino that took a sh*t ton of grief for being named Fernando. His name got shortened to Ferny. Nice kid, but I always felt bad for him. They should have just named him Eric.
Dexter sounds very silly to me and makes me think of This Guy or This Guy from the Past
Emmerson sounds pretty good. A lot of boys are given family names or last names as first names. Please do not name a girl Emmerson, or when she develops breasts, she’ll never hear the end of the jokes like “Hey, emmerson big boobies!”