Well I got tired of waiting and just decided to trust my ears. I reversed the hookups and got a hollow sound, so it turns out that the dash does in fact mean negative. If anyone was wondering if you can simply cut off the jack, strip the wires and hook your K340's up to the speaker outputs on a receiver it is possible.
But the preferred method for hooking up the K340's to speaker outputs is to re-terminate the end with an XLR or re-cable with an XLR and then use different adapters for hooking up the cans to different amps and outputs.
Apparently it is not advisable to use an adapter like this one: http://www.ttvjaudio.com/Banana_to_1_4_Headphone_Jack_adapter_p/the0000005.htm
I think the reason why there are hardly any adapters that do 1/4" to speaker outputs/banana plugs is because the difference in separate ground vs common ground.