Does anyone have any experience with computer shops that provide custom pc builds? I've seen a few ads on Facebook recently that seem surprisingly cheap. How likely is it that they keep costs down by using secondhand parts, for example? Or am I being overly suspicious?

Hi, looking for almost the same thing here.

Been trying local shops like Chantra, whatever you do DO NOT GO there, do not be tempted by the super cheap price. Their after sales support is horrible, even without the language barrier most of the time they are rude.

Try out:

One Gear
TK Custom
SDach Game

but if you really scared of getting ripped off by fake things. Go premium with a brand new DELL optiplex or precision, just add a decent video card and SSD. There are a few official carriers of Dell around.