I heard the Emerald Physics C2S in both rooms RMA and Modwright at CES 2008 and really like the sound of these speakers. But you need to have a best modified Beringer 2496 crossover to get a sound like that I will double check my budget first (RMA sells for $4000).
I probably wouldn't spend $4k on a $300 device either, but I've seen at least 5 different DCX modification packages well under $1k just this week, giving you many reasonable options. The notion that you MUST pursue these upgrades to enjoy the CS2's is just not true as evidenced by the many people who bought speakers after listening to them stock. I doubt many of them even gave mods the first thought.
Along those lines, I would add that quite a few here have taken a $300 device (the Slim Devices Squeezebox) and spent many times the retail price in modifications. It may sound crazy to some, but those who took the leap now enjoy a quality of digital playback previously enjoyed by a precious few.
Modifications are only a requirement if the owner deems it so; there are no absolutes. That said, in the minds (or perhaps more accurately, to the ears) of some, the results really are worth it.
I'm one of the "some", but as is almost always the case with this hobby, it's JMHO...
Perhaps the most interesting comparison would be the two hot speakers of the moment: the Emerald Physics and the Timepiece Minis. They are both in the same price range but of starkly different designs.
-Roy
The OP also mentioned the fact that
"both are tall slim floor standers, and both are extra-efficient." Since the Minis don't share those characteristics, perhaps your suggested comparison would be best made in a separate topic.
It would definitely be an interesting comparison IMO, though I'm not aware of anyone who's heard both.