You mean the impedance switch on an avr? That doesn't really mitigate impedance issues, more like complicates them...general advice is to run them at their higher impedance settings to allow amp to have full power. What Yamaha receiver models did you use? Where does the bi-amp come in?
The switch you see on the right is a set of resistors in the circuit to mitigate dips in response curve. This was on the Kappa 9(a), which was the last year of this speaker. When engaged, nearly any amp can drive. The downside is sonic purity must be compromised. I have listened with switch set to extended which is where the low impedance values come into play. I have an R-V2700 which was the last year prior to cheapening the power supplies. I have just purchased a CX-A5200. I ran an outboard Adcom to drive this speaker but when using Yamaha gear which is set to around 1 volt of output and the amp wants to see 2-3 volt as the 565 does, it does not work well at all.
Just teasing a bit, just hard to recommend amps without knowing the speakers. I love the Horizon (have a set of Sierra1s, a set of 170SEs and two sets of 200SEs), not really familiar with the Kappas.