Ok, I will give a quick reply then follow up later once I have more details.
If you are targeting mainland China than your best to host from within China, this is because of 2 reasons:
1) Internet speed within China is often 10mb/sec so users really notice the difference between China and non-China sites. Now having said that there are 2 Internet providers in China and they hate each other, I know that there are hosting packages that run your site on both pipelines, but often you are on one or the other, and the other will reduce the speed.
2) If you are hosting withing China you don't go through the international firewall and are not at risk of the firewall turning your website off.
Now hosting in China does mean all your data is accessible by the government, plus there might be some other issues if you are doing certain types of business, but if yours in line with the rules and ok with the government looking over your back, hosting within China will be the best for your users.
Hosting in Hong Kong, Taiwan or South Korea are your other options, they are all past the firewall so speed will be greatly reduced and you run risk of getting blocked at the firewall.
Thanks to Google's new settings in the Google Webmaster Center you can host anywhere in the world and your rankings in Google China wont be effected as you can change your settings to become a China targeted website even if hosting in the US.
As for trustworthy hosting providers that's what I need to get back to you with, there are a lot of people offering hosting, but due to the regulations I don't have any of my go to companies based in China, but there are good China companies I just don't know them off the top of my head.