Careful with wattage calculators, they are trixy. A fan, even an older one, generally runs 0.5A or less, that's 24w for all 4 fans. Your hdds will pull @30w each, so maybe 250w for all that. @100w for cpu, 350 so far, another 75w for mobo, 425w, and not knowing the gpu model, I'll guess high at 250w. So that does put the calculations right at 650w. Here's the kicker. There's 7 hdds,gpu and cpu that will never see 100% usage at the same time. Ever. You'll use 1,maybe 2x hdds at any given time since you aren't using an over the top raid system. So that @210w is in reality only 60w tops. You might use the cpu to 100% or even the gpu to 100% but not together or anything you are doing will be seeing 1-10fps or be so slow as to take 20 minutes to open another web page. So that 350w for both will be a lot closer to @250w. In reality, during anything kinda heavy usage, you'll be topping out somewhere around 450w at best. I'll bet with a 648w load, that calculator recommended something like an 850w psu.
Even with capacitor deterioration from time and usage, I don't see an issue with either psu being able to power your pc, especially considering your little sisters gaming/surfing/youtube/netflix/Facebook habits will only be running that pc in the neighborhood of 350w on average.
While that calculator was somewhat accurate in prediction, it only applies to absolute 100% usage, which is about physically impossible to achieve.