One of the selection criteria that I'm struggling with is that the server must be physically located in Korea: in my experience it's the only place that had an acceptable ping when accessed from everywhere my business operates (South East Asia, Far East and China, China being the biggest offender in terms of poor web access. We work from remote industrial areas so your experience of accessing the web from downtown Shanghai may not be the same as mine).
If you need to have good access in China than you have to host in China.
The Chinese Firewall slows down traffic that goes over the Chinese border.
That's why Google was physically located in China and there was the debate about Google leaving China. If you could just host outside of China and get a reasonable Ping in China Google wouldn't have had the trouble of physically being in China.
When Google moved "outside" of China they moved their servers to hong kong.
Maybe Hong Kong is a good location for you as well?
Depending on the money you are willing to pay it might also be worthwhile to have two servers. One in China and one outside of China and let those two sync with each other.