You should not be using DVC speakers in surround sound areas at all. The entire point of DVC speakers is to get stereo from a point speaker location. Like a laundry room or something like that.
If you only have two conductors, then you can only send mono, or one channel (either left, or right) to that speaker. If you use a DVC 8 ohm speaker, it will operate at 4 ohms or 16 ohms depending on how you wire it. But, you aren't sending it stereo. Just mono and I would typically use the pre-outs of the AV receiver and set it to mono, or use a stereo to mono summing adapter, then send it to a decent single channel of an amplifier, or a multi-channel amplifier on the BUS input to that every distributed zone could get audio properly.
Since nothing can benefit from DVC speakers, I would not use DVC speakers anywhere at all to begin with. I would still run everything as mono that isn't getting proper stereo to the room. Not sure who did the original installation, since music has been stereo for more than the 20+ years I've been in the business and another 20 years before that. Basically, anyone that designs a distributed audio system, and doesn't plan for stereo, at a minimum, in each zone, does not know what they are doing, or they planned specifically for mono in each zone from the start, which is perfectly acceptable if that was the plan. Nothing really wrong with mono audio for background music in a room for casual listening.