Here's a couple power supplies that might interest some of you (that are willing to put in some extra money for these features).
http://www.thortechpower.com/product-24.aspxThis Thortech (Geil) Thunderbolt Plus 1200w (GOLD) has a display that shows you info. from the power supply like wattage going through it etc. (It's single rail, even though some early literature stated multi-rail). Good for S3's on one power supply if they aren't overclocked.
http://www.amazon.com/Thunderbolt-Supply-iPower-Certified-TTBPK20G/dp/B008BCFZLI/ref=sr_1_2?s=pc&ie=UTF8&qid=1410392221&sr=1-2There's also a 850w version (although it's mismarked as 1000w on Amazon.com). It looks like they showed a Platinum version a couple years ago, but it never came out.
http://www.thermaltakeusa.com/Power_Supply/Toughpower_Series_/Toughpower_DPS/C_00002390/Toughpower_DPS_G_1050W/design.htmThermaltake has the new DPS G (cheaper that the DPS series that came out last year) series, that when hooked up to a computer via USB cable, will show you the wattage and used power, calculate electrical costs etc. and has a app. also. the top of the line is the 1050w (GOLD). This will only work if you have it hooked up to a computer though. Good for 2 overclocked S3's on one power supply, but you'll need a splitter since there's only 6 PCI-E connectors.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817153214&cm_re=1050w_DPAS-_-17-153-214-_-ProductNote, both of these are not cheap power supplies, but if you find that you want something that monitors the power going through it, you may want to consider them.
If money is not a factor with your initial investment, the Corsair AX1500i 1500 Watts Power Supply with Titanium Efficiency (CP-9020057) costs $450+, but if you wanted to keep your power usage down to the absolute minimum, this power supply with 2 S3's (that would be at about 50% load, so peak efficiency) would be it (especially on a 230v line).