Just be aware that you get what you pay for. I have experience with these specific converters, and many of them have no thermal protections. If you overdrive them (e.g. more than 1/3 of their "rated" capacity), you run a pretty high chance of burning them out.
I've used those before, they have a horrifying amount of noise on the output, lots of RF noise, and a very audible high-pitch whine. They also overheat very quickly even at half the 'rated' load.