Buying a computer in Beijing?

[calamindos]

I'm considering buying a high performance laptop, desktop computer , or spare parts to build a PC either in Beijing or ordering from USA and having it send by a friend. Prices in China seem to be quite higher than in USA, however I don't know how much duty I will have to pay here if I get the package sent from USA. I know some computer shops abroad that order spare parts from China to sell in their shop, so would it be better to buy reliable spare parts here? Or a pre-built desktop computer if there is less tax on them? Any help would be greatly appreciated.