an arranger kb tyros or s series, korg pa4x/pa900, BK9, and a synth workstation Montage, Motif, Kronos, etc, is the way to go you can cover almost any musical project that way...there is no need for two arrangers Imo..
I fully agree, even better if one of them has 88 keys piano action and the other has top of the line synth/organ action.. Also i am a firm beleiver that having two different brands adds more diversity to your sound..
But then, the OP is asking for a single arranger keyboard....