I must add this for posterity.
The reason I chose the CA-1a (and soon the SR as well) was because they are truly open. Apart from those two there's just the Mysphere that I know of (and its AKG inspiration). I simply cannot stand the sound of pads, even in the open-back headphones, and that audible reverberation coming from the sides of the pads immediately suggests to the brain that you have "put headphones on". None of that with the Requisites. That is the reason for that "floating inside the soundfield" sensation that many have shared – simply because you don't hear sound bumping off the walls. For someone like me who swears by the studio monitor sound there's simply no other alternative. Every other headphone that I have tried has that audible reverb/decay, including Dan Clark, Abyss, Audeze, all of them. So I find it quite sad that all-around pads in the 1995 is the evolution we've got and at the same time I'm very grateful to the team that brought us the true audio marvels that the CA and the SR are.
There are of course IEMs and they're a different story in some ways, but as far as full-sized headphones go, the original RAALs are the only choice if you don't want to listen to your headphones, but want to listen to the actual sound instead.