OK, I see. In that case, since you essentially will be sticking with four channels in that 4200 amp, you can look at the Linn floorstanding Ninkas speakers, which can be driven aktiv with four channels - using one stereo bass aktiv card card on two channels of the 4200, and one stereo treble aktiv card on the other two channels of the 4200. The Ninka is the speaker that preceded the 140. You can buy second hand Ninkas and the aktv cards for about $1,000 together. Many people prefer the Ninkas over the 140s, so, though it's a matter of personal taste, they are of the same class of speaker. So that's what I would do in your shoes.
For more specific info about creating a chain around the 4200 amp, go to the forums at www.linn.co.uk. The members there can give you spot on advice re: all the details.