Just to clarify some. (Talking about USB2.0 as 3.0 has a little higher power)
The USB on computers are powered by the motherboard (if not using extra PCI USB card).
Usually the motherboard gives about 500mAh to each USB host. If that host has 4 USB connectors all those connectors share the 500mAh.
And just be careful to not go above 500mAh as some (older) motherboards or even add in card's cannot handle the extra power and will fail to work(permanently).
So a charge-only cable will not make a difference in this situation, same goes for using multiple USB ports as that also brings extra problems with it, as power/voltage doesn't flow in just 1 direction (when using 2 poles). You could blow out USB voltage regulators when connecting different USB power leads together.
As for the phone side you can also use a 5000mAh power source, as the phone will 'take' what it needs. For DHD the max charging power is about 800mAh~900mAh if I'm not mistaken.
As long as its 5V and somewhat stable.
So if you want to charge the DHD (or any other USB chargeable phone, mostly all of them) as fast as possible use the original wall charger.
If you have to do it on the PC/Notebook unplug as much USB devices as possible, so most of the power can go to the phone.
Also make sure the screen of the phone is turned off as that's the biggest battery drain of the DHD. Thus also making charging slower (when on).