In both cases, madali lang ang upgrade dyan.
You can purchase a PCIe x1 USB3 card then voila! USB 3 ka na (mga 1-1.5k yata itong USB3 card).
Or you can purchase a SATA-to-eSATA cable, and ipa-gapang mo na lang through the rear of your HTPC, and into a vacant SATA port on your mobo. Eh di puwede ka na eSATA. Below P100 lang dapat itong eSATA to SATA cable.
I prefer the eSATA route. Mas mura kasi. And current real-world tests still show eSATA with faster transfer speeds.