Honest speaking, buying online such as amazon in US is a gamble one have to take. It is definitely not worth to have the savings that is very small.
TS, you are buying an extreme mobo, if you can even afford an extreme rig, i dont see what is it about paying a few bucks away from SG prices with the ease of mind of having a local warranty support.
Tips to take note:
Buying CPU and Mobo overseas do not entitle for free shipping to SG. And you will need a forwarder to ship to SG. Only certain AMD and Intel CPUs MAY be able to ship over to SG.
However on a side note apart from GST to factor in. The cost of shipping a mobo + CPU over to SG is usually a standard rate of $16.70USD OR $19.55USD assuming you are using HSG or CGW normal shipping rates and depending on certain boards that comes with lots of accessories or in some case lower end boards will pack with lesser accessories usually will fall under $16.70USD to ship over. High end - $19.55USD.
So SG sells ASUS X99A + i7-5820k ~ $888
Amazon is selling X99A $247.99USD + i7-5820k $369USD + $19.55USD Shipping thru forwarder, Including tax ~ $885.43SGD.
Total Savings less than $3. Really bo hua.