B & B,
Unless you're in a large room or listen loud enough to break leases or get the police knocking at your door, 30 wpc will not require highly efficient speakers. My rule of thumb for enough power is to reach a continous 105 dB output. With two channels and a typical (roughly 2,000 cu. ft) room that works out to needing about 105 dB (speaker efficiency rating plus amp gain). So if the speaker is rated at 92 dB/w/m, you'd be looking for at least 20 wpc (13 dB of gain). Listening nearfield or using a powered sub would only help in this regard.
Single driver speakers provide a coherency that other speakers cannot match, especially nearfield. By definition they are "active" meaning one driver per channel of amplification, which is another huge advantage. And there's no crossover to screw things up, especially near the precious midrange. But there's no free lunch. Deep bass is very hard to come by. Output is limited (but to sane levels). Extreme high frequencies need help (whizzer cones, etc.) or beam like a flashlight. The magic of single driver designs is in covering the essential 80 - 8,000 Hz range with the simplest/purist of solutions.
Both the Omega XRS and The Horn sit pretty low and can get lost behind furnishings. In my experience The Horn can sound very nice, but very fussy regarding balancing room bass gain. Anything Louis builds sounds wonderful. It amazes me how good the relatively cheap Fostex FE127E driver (that the Super 3 and XRS use) sounds.
OB's provide a completely different listening experience, trading pin-point imaging with room filling (actually more natural) sound. My brief experience with OB's tell me that you need lots of open space for them to work their best (minimum 15 ft wide by 20 ft long room with the speakers sitting 5 ft out into the room). The Hawthone Iris gets down to 40 Hz without the complication and expense of the Augie (which can be hard to believe until to see the 15 inch driver and hear it).
We'd need to know your musical taste before making specific recommendations.
