Well you have a modular psu which is good so only install the cables you need.
When thinking about cable routing people can get obsessed with running cables behind the motherboard when there is plenty of space in other areas.
A very over looked area is sata cable length, most people use the long sata cables that come with the motherboard then get into a mess with tangled cables all over, keep your sata cable length to a minimum, you can get very neat short sata cables to connect your hard drives and you don`t need an excessively long cable for disc drive.
you can also route you case connection cables, a lot depends on your case where the cable routing holes are located.
What kind of case do you have ?