Its for this reason i use straight-through extensions when builing my PC. Lets me route cables where/how i want. Then they connect to the psu cables somewhere sensible and hidden. Adds to the cost but makes the whole build (so upgrades/replacement) so much more modular.
Just have to make sure you get decent ones and not thin core cheap crap.
I almost did the same as you, and decided to beep out some of tge psu cables as i was waiting for the new PSU to arrive. Immediately bought straight extensions, and havent looked back since!