The picture with the grill removed shows a driver that looks a lot like the Harman-Kardon Odyssey—these were used in most of Apple's CRT iMac models, some of the company's computer speakers (notably the Soundsticks and the ones that looked like champagne flutes), iPod docks, and maybe some car audio and full-size speaker designs.
They always sounded surprisingly good in my old iMac, and had a frequency response similar to what you describe. If this is what NuForce is using, I'm not surprised it sounds great for the size.