After digging around a bit more, I found a few things.
A chart listing power supplies and their amp ratings, etc. It stated that the EA650 was rated at 45A, which is slightly above what I need. I'm still curious as to why it's listed at 45A, though.
Then, I found:
43-54 amps - Often "650W" PSUs
This range is a good choice for the gamer with two moderate video cards or one very high power card. Start adding in a lot of hard drives, fans, water-cooling... and you might be more comfortable in the next range, especially with moderate overclocks of the CPU and GPU(s)
This basically puts my mind at ease, but I'd still love a response confirming that my system will be working properly.