I suggest you look at it again, as the SS-650AM has 53A. If it was 63A, that unit would be more closer to a 750w as 63A on the 12v is 756w. Edit: since you had noticed it. Ok, but the fact that you are complaining about the 3.3/5v is rather silly considering that modern day system draw very little from it and the majority of it on the 12v. The Capstone also has a 5 year warranty. Not a 30 day...
I'm not sure what you mean by the "overall statistics" it "outperforms" the Seasonic G and Rosewill Capstone. What statistic you are basing this off of? The fact that you thought the 650w unit as a 63A on 12v? I have no problems with going with a lower capacity unit, if the quality of the PSU is better in respect to design, electrical performance, build quality, etc. Like for example, I have no problem going with the Rosewill Capstone 450w over the Seasonic S12II 620w. As well as I would get the Seasonic G (any of them) over the Antec Earthwatts Platinum.
While it would be awesome to only look at the efficiency rating to determine the quality of a PSU; however, that's not the case. There are Platinum/Gold units that are worse than Bronze units. Efficiency is only one aspect to a PSU and is typically is treated as a secondary feature to a PSU overall quality. What you should look at is the overall topology design, voltage regulation, ripple/noise suppression, response to transient loads, build quality, audible noise, etc. This is not something that you can simply look the label of the unit provided to you by the manufacturer. This is something you have to do research on and read proper, competent reviews from those who open up the PSU to analyze it and test how well it performs with equipments that cost a few thousand of dollars.
Edited by qwan456 - 6/7/13 at 11:45pm