Apogee vs Soundlab

If both speakers are connected with top notch electronics, definetely the Apogee.
More punch, more depth and realistic soundstage

Definetely the CAT Signature makes the sound sharper etc.
Conrad Johnson is a much better choice, softer more musical but unfortunately not too realistic(typical golden sound)

Yes it is true, it is very difficult to get good sound of the Apogee Diva, most amplifiers will not sing beautifully(also some expensive one's), it is far more easy to drive a Soundlab.
But once you have matched your Apogee with the dedicated amplifier, then it will be unbeatable.
Apogee is the most difficult speaker to sound beautifully!