Taiwanese brand of computers called 嘉馬電腦
Is 嘉馬電腦 a normal-sounding brand name to Chinese-speakers?


Yes, while I do not know this brand, it sounds like the kind of names a native would have made. You want your computer to run fast, like an auspicious horse, presumably.


  Is this a reasonable translation?


No, because it would be difficult to make out what is the original Chinese. For proper nouns, it is probably best to use a romanization (e.g. pinyin) along with original characters in Chinese. 

I would translate it to "Jia Ma Computer (嘉馬電腦)", or if the meaning is important, "嘉馬電腦 (lit. The Auspicious Horse Computer)"