If you want to look at network branding, take a gander at the Gawker spread of sites. Kotaku, Jezebel, Lifehacker, Gizmodo and io9. All with their own names, URLs and communities.
They're for different audiences and marketed to them specifically. Not as generic, lump-based chunks of a whole. But all recognizable as part of the larger Gawker umbrella.
It's not ProductivityPorn.Gawker, it's Lifehacker.
Rely on quality results being returned in searches. Not on lazy brand marketing.
If you can't work out a good name, just don't graduate the site outside of its beta period.
Don't make people think it's full-fledged by leaving the non-sketchy design in place. No matter how nice it looks, giving an SE site its own look but denying the community to champion it with a distinct, non-subdomained name (however bad) is being two minds of branding and building.