It often comes up on the AC forum and in dealing with customers: "what are the differences between the 3, 7, and Alnico series speakers?"
My conclusions are based on having tube and SS amps in front of the Omegas, and the systems in various venues from quite live to quite dead acoustically. All will run well on a watt and a half. YMMV.
Concerning imaging:
All Omegas image insanely good, often extending beyond the outside left and right of the speakers. They play well with all types of music in all kinds of environments, not just intimate nearfield "girl with guitar" type situations. All Omegas are also very fast.
3 Series: Electrostatic speed, huge presentation for such compact speakers with a single tiny driver, clear defined well focussed pinpoint imaging, very transparent and revealing with incredible detail. Hearing what comes out of such a small driver will play with your head.
7 Series: Fast, dynamic, punchy, fuller sounding than the 3 series. Top end closer to the 3 series than the Alnico. Soundstage a little deeper than the 3 series, but not quite as defined. Greater texture than the 3 series and can go louder than any of the Omegas I've heard. Aside from the new 8" coming out they are the most efficient. Happy with all types of amplifier.
The Super 8: I haven't heard it yet, but Louis says it sounds like the RS5 on steroids, and with more dynamics. Also very efficient at 98dB. One of the prettiest drivers I've ever seen in some of the most beautiful towers Louis has ever produced.
Alnico Hemp Series: Really in a class by themselves. Rich and lush, tonally very even and non-fatiguing, incredible tonal density layering and texture, deepest and most ethereal image of all the Omegas, the most refined, and the best rendering of bass I recall hearing. Smooth without sounding rolled off on the top end. Complex music is a cinch. The most addictive Omega I have ever heard.
The High Output (HO) Series: These take the sound of the single driver version to the next level in dynamics, and in their ability to play more complex music. They still have all the excellent properties of a single driver. Nothing is lost. Everything is gained.