First option:
When i had only one S7, I ran it with two 850 watt Corsairs. I connected each PSU to two separate 120 outlets which had wattage to spare. I had no probs.
Second Option ( will cost you a bit and you lose access to your Stove or Dryer. Hope your wifey can cope with that.):
Later on, I hooked a cable to my stove outlet. Then, I ran it to a PDU. Now I have 4 rigs running on that circuit with no issues. Pretty sure, i could run 5-6 S7s with the wattage capacity from that circuit. It cost me about $200 for the cable, male and female connectors and the PDU. However, i got a great deal on the PDU. Another guy had been using it for the same purpose but decided he wanted his stove back. So he sold me the PDU.
Third Option ( most expensive) : Hire an electrician to set up a dedicated 240 volt circuit like you have for your stove.