Hi Phillip,
Correct, I run 6x S3 at 150Mhz undervolted at exactly 1090w on the wall (GHash.io reports a 1.85 TH/s dally total ). Not sure if 200 watts headroom is save ( I think your suppose to stay 25% under the maximum rating at continues usage ).

I tried undervolting 193MHz-200Mhz but it only yielded 380Gh/s at 280w was not worth it in my opinion. ( the gain was only 20w ) and noise and heat was not much lower.

If you shot me your email in a pm I canemail you some photos and simple instructions. If you done a S1 pencil mod you should be fine, but if not it might be a little more you bargaind for.