The KEF2005 is not a single driver design. KEF calls is a "Q" system, I call it a coaxial. The speakers have center mounted tweeters (where the dust cap on a driver usually is) and a crossover of sorts.
With all things being equal (never happens this way:-) a good single driver design will offer more discernible reproduction of speech (a big plus when listening to movies/TV). The downside being that they do not have the HF extension of most multiple-way speakers that use a tweeter.
Although a fan of single driver speakers they are not always the best choice.
Having played around with building a small 2-channel HT setup for our bedroom over the past 6 months I finally ended up using coaxial drivers (center mounted tweeters) instead of single drivers.
The room (rugs over carpet, comforters, wool blankets, a gaggle of down pillows, stacks of clothing that never get put away, etc.) is so dead acousticaly that for the best overall sound tweeters are needed.
As the system is for HT/TV use only I am now toying with the idea of adding an inexpensive multi band equalizer to the mix (see them quite often @ the thrifts) in order to better tailor the sound to the room. Not a Hi/fi approach, but then it's not a Hi-fi system.
I picked up an old Carver receiver with bass/mid/treble controls which is what gave me the idea. The tone controls on the receiver, though helpful, do not offer minute enough adjustment.