Are you actually going to Hong Kong?
If so - an afternoon around Kwong Wah street is akin to nirvana. Mind boggling selection of dozens of RC shops staffed by racers that really know what they're talking about. Prices are very competitive with each other.
I can personally vouch for Action Hobbies as being excellent - great helpful staff, great selection, and competitive prices. Hobby Hobby, Challenger, and Harmony are also amazing. Each shop has a slightly differnet focus though. It's awesome.
http://maps.google.com/maps?f=q&sour...,0.004128&z=19
If you're looking for online retailers - the guys listed in the post above are all excellent.
RCmart is a big supporter of offroad SC racing at the moment in the region, and sponsors a 4x4 slash cup series. How cool is that?
Cheers,
Ty