Dazzdax, to answer your question about the differences between the Sound Lab and the Apogee, IMO/IME the Sound Lab is likely the better performer of the two, given that you have the ideal amplifier to driver either one, which could be two very different amplifiers!
The reason I say this is that the Sound Lab has a powered system for moving the diaphragm and the Apogee relies on a permanent magnet. All magnets in all speakers have a certain amount of sag when the amplifier puts power to the diaphragm to make it move (BTW this is why Alnico magnets are preferred in cone systems as they sag the least and consequently sound better). IOW the powered electrostatic field of the ESL will not sag while the permanent magnet system will. The cone speaker equivalent of this is the field coil; so far I've not heard of a field coil-powered magnetic planar, and that would be an interesting speaker project...
The powered system offers greater impact and greater detail, often with associated smoother sound, IME.
Otherwise I would expect very similar performance overall, if it is possible to rule out the amplifier in the equation, which I am not sure is possible.