When it comes to PC speakers these days, separate subwoofers that sit on the floor are out, built-in subs (or no sub whatsoever) are in. Altec Lansing's playing up the whole built-in sub theme with its modular FX3022 Expressionist Bass speakers, which come in a black and white and will carry an MSRP of $129.95 when they're released in October.
The company's marketing material says the Expressionist Bass features twin-desktop speakers with 4-inch subwoofers built into the base of each speaker. There are separate 1.5-inch drivers for mid and high frequencies, along with an auxiliary input for connecting MP3 players. Power and volume controls are on top of the left speaker, and in case you're wondering about their size, they are 10-inches high and 5.25-inches wide at the base. I've seen them in person and they're definitely striking.
It's worth noting that these are not USB-powered speakers--they simply require too much power and so draw juice from your typical hefty AC adapter. But the good news is you don't have to worry about a subwoofer cluttering up the floor by your feet.