IME the only differences in that range of amp are the "bells and whistles" such as CD/mp3 input, headphone out, and tone-shaping circuitry.
If you're looking to buy in the 15W range, I'd endorse a plan to spend the least you can. Generally an amp is where you want to splurge, but in this case keep it cheap cuz there's not a big payoff in the quality of sound.
I dunno Singapore, but in the US there's basically no resale value in the 15W range, cuz they come free in the typical starter packs that surface every Christmas.