You know you can get 5 s3+ for 1450 based on 500 per btc. which is 2.2 th based on 453gh each and 1775 watts. so pay extra for less power but about 475-675 watts less in power consumption sure. Throw that money away.
i have my s3 occupying all my power supplies. assuming that I need 2 EVGA 1300 plus one CX500-600 to run 5 S3 (overclocked), I will have to pay extra $380 at the minimum, so your math does not compute, pal.