Been following this USB 3 discussion and did few tests with the T3500 using a cheaper 256gb stick (seen in purple) for redundant storage, so it will not win any benchmark contests. But it gives us an idea what's going on.
First image is benchmark on internal USB header just below the PCI slot. Speeds same with headers in back of case and front panel. Second image is same 256mb stick connected through
this Inatek 7 port PCI card. Also moved a few very large video files around and results were about same - roughly 3 times faster than the T3500s 2.0 headers.
Top two motherboard PCI slots are incompatible with the PCI card physically. So ... with this fat gaming GPU only slot available was the bottom one. Card is powered direct from the Dell PSUs 4-pin molex by way of SATA adapters run behind the GPU.
[edit]
Win10 drivers for the card were downloaded direct from the Inateck website.