I bought my parts from amazon also. Not all of it. You need to do your research. If the cost at the end is the same, its better to get locally. RAM prices are about the same. The only parts worth getting i see is SSDs, and GPUs.
I bought my GPU, and heatsink and ram from amazon, the rest of parts from SG. GPU was EVGA gtx780 SC. Warrenty international, so send back is to taiwan, not too bad if got issue. In the end the thing is, if your parts got no problem, you win. If need to send back for repairs, then it depends.
But dont have to worry about DOA or defects as amazon's customer service is top notch. They'll cover the costs and stuff. I even heard of amazon waiving a shipping charge for someone's TV before because the customer asked. lol!
So in the end, to make your decision, check and see if the parts you get locally vs amazon, is the savings about $150? if not dont bother.
Oh ya, $400 sgd and above got additional 7% singapore gst
Mobos dont ship directly to sg, thats why savings not as big because u go thru concierge service. Unless they start shipping to SG directly, I would get my mobo+cpu from SG cuz got bundle price. Again, do your own research. Theres alot of checking, double checking and recalculations from shipping, tax, etc