Is the cable management/modular worth the investment?
I personally would not bother with modular since it adds to cost, adds a possibility of mechanical failure and a possibility of losing the spare cables by the time you need them. Also, cheap cases with bottom-mount PSUs and no motherboard cable management usually have plenty of space to stash cables behind the 3.5" HDD rack.
For top-mount PSUs, you can install the DVD drive in the 2nd 5.25" bay and stuff unused cables in the 1st one. It might not look pretty but it keeps unneeded cables out of the airflow which is all that is really required.