Everything is connected. <- This sentence has more meaning then it may seem to pose.
The person who posted that response you directed to me in private is correct, technically. But I don't agree with the sentiment of it. Because going out of usb bandwidth with just a few usb audio devices, even if usb 2.0 only, is going to be nigh impossible. You would have to defeat 480mbit every second. Usb 3 ups this 10 times. Windows kernel for audio is and has been rewritten, its an on going thing. I do however think you could have a bad usb controller, and sometimes a connected usb device can cause noise on the system and problems for other devices. So its not a bad idea to separate things where possible like the suggestion you received already.
On a side note some usb chipsets are very bad, historically speaking, but most are quite ok now. Some of the old bad manufacturers are still around, but hopefully they will die off soon.
If there is one area here we want only 1 manufacturer, it's for usb. It should just be a single vendor of it, preferrably with the major companies chipping in money for invention and such, but a dozen developers of system drivers for the same thing - that has to die. We're getting there tho.
Please keep to your posted thread and dont mix in pm - others can have same issue as you so help others by keeping it to the thread.. People post thank you's all the time to long gone thread saying they had just the same problem and they found the solution or path to it thanks to the thread.
Don't make more topics of the same thing, not everyone can be helped, often because of refusal to accept help, lack of resources or communication barriers etc.