With Amazon reportedly poised to launch a tablet computer, technology research firm Forrester is predicting the device could be the first legitimate challenger to Apple’s iPad. Forrester Research analyst Sarah Rotman Epps, in a blog post accompanying a report released Monday, said Amazon taking on Apple is a “bit like David taking on Goliath.” But Rotman Epps said Amazon’s “willingness to sell hardware at a loss combined with the strength of its brand, content, cloud infrastructure, and commerce assets makes it the only credible iPad competitor in the market.” “If Amazon launches a tablet at a sub-$300 price point – assuming it has enough supply to meet demand – we see Amazon selling 3-5 million tablets in the fourth quarter alone,” she said. The Seattle, Washington-based Amazon, maker of the Kindle electronic book reader, is capable of “disrupting not only Apple’s product strategy but other tablet manufacturers’ as well,” the Forrester Research analyst said. Apple sold 9.25 million iPads last quarter and dominates the market for the multi-media devices, which are also being produced by South Korea’s Samsung, Blackberry maker Research In Motion and scores of other companies. But none of the iPad’s rivals has managed to put a scare so far into the California-based gadget-maker. Amazon has not publicly announced plans to produce a tablet but numerous press reports have said the online retail giant will come out with one this year.