So since there's only 3 of these would I be ok to run one overclocked using 2 cables? And the second s3 on the third?
The one you overclock I would suggest upping to 12ga wire on the main, and 14ga on the extension, but the wattage is there, so you could do it easily. Remember, 5% +/- on the wattage draw for estimates is fine until you burn up a brand new miner. Start at standard clock and if you have an amp clamp, use it. I would NOT suggest overclocking both on less than a 1200 watt though.
Also, the Rosewill is rated at 100k mtbf at 25c. but it lists the supply at 100% rating stable at 50c. E-mail them and ask them what the average lifespan is at 40c.