Running the ~£75 StarTech PEXUSB3S44V card with zero issues in an old PC which I have listed below. I don't need to bother with drivers as Windows 10 supports it out of the box. I have also found that leaving power management set to balanced is fine, no disconnects so far. I get true full bandwidth USB 3.0 from each port and if I need more then I should be able to split each using a hub. Not that I would ever need to but I could have HD TV playing beside a HD webcam stream while playing a game in the rift.
You can get away with using a USB 2 port with the rift but why would you want to? You go from USB 2 480p to USB 3 720p, 50% more which covers both accuracy and smoothness of tracking.
Although it's more expensive than other solutions, it is way cheaper than a new CPU, motherboard and RAM to natively support the Rift. Considering the age of my PC the StarTech works out as a steal. When the next node shrink hits I will go for a Ryzen setup and should be able to simply swap the card to the new machine.
3770k @ 4.5.
Noctua NH-D14.
GA-Z77X-D3H Motherboard.
32GB of DDR3.
EVGA 1080Ti FTW3.
750W XFX PSU.
Sandisk Ultra II 480GB SSD.
Sandisk X300 512GB SSD.
2 x WD Black 1TB.
DVD Writer.
HAF XB (Dremel'd to improve airflow and fit a magnetic dust filter).
2 x Noctua AF-140 fans.
Noiseblocker 120 fan.
USB Bitfenix Recon fan contoller with sensor placed inside 1080Ti heatsink.
USB Oculus Rift + 2 sensors, wil decide on 3rd / 4th after moving office/bedroom.
USB 3.0 card PCI-X 4 port/4 controllers (dedicated to the Rift).
USB 2.0 card PCI-E 7 port/1 controller.
USB Hauppage HDsolo TV Tuner.
USB Gamecom 788 7.1 headphones.
USB MS Lifecam.
USB Strafe RGB MX silent with USB passthrough.
USB Logitech G502.
USB Xbox controller.
USB UPS.
USB barcode reader cradles x 2.
2 free front facing intel USB 3.0 ports for removable storage.