They will work, but the speakers are going to be putting a bigger load on the receiver. It should be fine, but just make sure it doesn't get too hot. And I wouldn't listen for extended periods of time at high volumes, that will put a big stress on the amps.
The only switch like this I've ever seen on a schematic soley redirected the speakers when both A and B speakers were engaged. If it was set to 4, A and B were placed in series, set to 8, they were in parallel. There was no connection to the amplifier stage of the receiver.
Granted, my experience is limited (and pretty old). If I'm off base, someone please correct me.
I do not know much about the yamaha RX-V3000 but most decent receiver should be fine driving a 4~6 ohms speakers. If the power supply of the receiver is beefy enough it may actually produce more watts, a Sunfire receiver for example would be quite happy with that. PSB speakers are well behaved loads also, you should not have a problem with the yanmaha