Sunix
PCI Express x1 to 4 x USB3.0 port Adapter Card (USB4300)

Basic but good !

One thing to note up front is that this card (and probably all cards like it) needs auxiliary power to able to supply the four USB3.0 ports with 4.5W (5V/900mA) each according to the USB3.0 spec. This is in addition to the PCI Express connection to your motherboard. So you'll need about 20W spare capacity on your PC's power supply, and you'll need either an available power connector or a cable-splitter arrangement.

Sunix make 3 versions of the USB 3.0 add-on cards, the only difference being in the style of connector used for the auxiliary power supply connector. The USB4300N has an old-style 4-pin "CD-ROM" type power connector, whereas the USB4300NS has a flat SATA-type power connector. I'm not sure what connector the -IF card has, but you can see all three cards here :

http://www.sunix.com/en/product_group.php?cid=2&kid=34&gid=103

The card I received from Nivo was the USB4300NS (SATA), which looks slightly different to the one pictured here. I used it with an adapter cable to go from an available "old-style" connector on my PSU to the SATA connector on the card.

I had no problems commissioning the card. It is intended to be plugged into a PCI Express v2.0 motherboard slot, where it will use one lane (x1) to achieve an overall 5.0Gbps throughput. Technically each USB 3.0 port should be capable of 5Gbps, so logically this card can't sustain the full 5.0Gbps on all 4 ports at the same time. For all but the most demanding I/O applications, it will probably be quite difficult to saturate this card and experience a bottleneck. You can also plug it into a PCI Express v1.0 slot, but it will then only be capable of 2.5Gbps, which is probably still enough for many applications. I verified that the card fitted into a PCI Express v1.0 slot, but did not test in this mode.
If you absolutely want maximum speed, make sure to use a PCI Express 2.0x1 slot.

Apart from those caveats, the card works great. I comes with a brief leaflet and a CD with drivers, as usual the drivers were already a little out of date and newer ones were easily obtainable from the Sunix website. The driver loaded fine (Windows 7 Ultimate 64-bit) and works with no problems. For the technically-inclined, this card is based on the Renesas uPD720201 USB 3.0 controller, for which driver support is bog standard.

If you're reading this review after about mid-2016, perhaps look around for one of Sunix's newer cards that support the USB 3.1 ("Type C") spec. As at the time of writing (Nov 2015), there are only two such cards, and they only have 2 ports, however I'm sure that will change soon.

STRENGTHS:
1) Full USB 3.0 5Gbps throughput (when plugged into a PCI Express 2.0 slot).
2) Full USB 3.0 5V/900mA power supply per port (when used with auxiliary power connector).
3) Backward-compatible with PCI Express 1.0 motherboard slots (albeit at half the throughout).
4) USB ports are backward-compatible : they can operate as USB3.0, USB2.0 or USB1.0

WEAKNESSES:
None found so far.

BEST USES:
Adding USB 3.0 connectivity to an older desktop PC motherboard

SIMILAR ITEMS OWNED:
Sunix 2-port serial card

RECOMMENDED ITEMS:
Any of the Sunix 4300-series USB 3.0 cards