The 5V wires don't really matter if they are missing. The 24-pin ATX cable alone is completely ridiculous for modern day systems since it has an excess of 3.3V and 5V wires. A modern day system today under maximum load will typically only stress the 3.3V rail to about 2A (6.6W) and the 5V rail, depending on the amount of drives of course, but usually to only a couple of amps (10W). The 24-pin ATX connector has five 5V wires on it. Then take into account that hard drives don't even get their 5V from the 24-pin connector but they get it from the SATA cable. So all in all, 5V wires on the 24-pin ATX connector are practically pointless in a modern day system besides having one or two maximum. Some things like an add-on PCI wireless card will use the 5V. But it is virtually only used in hard drives (the spinning disc) and that is about it.
Upgrading to an EVGA 650 G2 would be kind of pointless to be honest. Keep the RM 650, it is a very good unit. The ATX specification is really due for a major revamping. I'm talking about reducing the number of 3.3V and 5V wires to a minimum on the ATX cable, maybe an additional 12V wire, and just getting rid of everything that is useless anymore. It would actually save manufactures a lot of money if the amount of wires could be reduced to something like 10.