I've always felt that, if you are going to have a two keyboard rig, that they should be from different manufacturers. TBH, although the BK5 adds some new kits and tones, it isn't enough to warrant being added to a G70 IMHO. There's just altogether too much that sounds pretty much identical.

I think a Korg or a Yamaha would make the better companion, at least EVERY sound would be different. And, because of the totally unnecessary roadblocks to dual arranger operation the manufacturers seem hell-bent on continuing to put up, I can't honestly recommend two arrangers. I would always feel stymied by the fact that I would have to chose ONE arranger as the style backing, no matter which one is producing RH sounds. No two different manufacturers make it possible to integrate full arranger operation from one keyboard. Codes to change Variations, trigger Fills and Intro/Endings, Break-Fill/Mutes, Transpose commands and most regular arranger features are quite unique to each manufacturer, and you are not given the option to change them...

So, in fairness, I would go with a modern WS/Loop player. For starters, their MIDI implementations are often flexible enough to set up reception of the arranger codes they might be able to use. Secondly, their sounds tend to be a lot more contemporary, and often of higher quality than many arrangers. And lastly (for now!), the loop and arp capabilities (for instance, Karma on Korg's or the chord following arps on Yamaha's) can add a tremendous amount of modern flava and attitude to an arranger's style output with minimal work.

I can see Russ's viewpoint of adding in only minimal sounds to an arranger rig, but unless your needs are so tightly regulated, why not go the extra step and add in a keyboard that not only does the organ and piano chores better than your arranger, but one that does so much more, too?