It feels like all the plastic surgery clinics are gathered in Gangnam, so it's inconvenient to go back and forth, and there seem to be a lot of quacks.
On the other hand, how's the neighborhood? It's not crowded and it's easy to get to, but I don't know the reviews. The famous places in Gangnam seem like they'll be tiring to wait in line and they might be a bit dry.
By the way, there's a Cocoxx in Magok District, but I haven't been there yet.