Yeah, I was thinking about attaching a huge Noctua if I end up splurging for one of these. (Unless you happen to have a better idea?)
Make sure the airflow is flowing along the fins. I looked at some images of one of the Startech units and there was a casing that had fins (possibly vented) on two sides, and it isn't entirely clear what is going on inside. If you can locate a teardown image of what it is like inside, that knowledge would be very helpful to selecting the best strategy. Or a FLIR camera to find the warm spots. Or even just the back of your hand. It may be obvious, and if so *great!*, but the bits that get hottest fastest need the best airflow over them.
The Startech unit seemed like the worst of the ones I saw, it appeared to be probably molded plastic with only the fins on two sides.
Hard to cool, because you probably really need airflow coming down both of those sides IMO.
This one looks like extruded aluminum, which is likely to give better heat spreading results:
And these two look like someone put some actual time and care into venting and cooling considerations.
None of this implies anything more than my superficial glancing at a bunch of images to pick some interesting bits out at first impression. The ones with significant fins or venting win only because I am more convinced I can "fix" cooling problems with a fan. It is specifically not a purchase recommendation because I have no idea about the chipsets used etc.
If their cases have standoffs that are in contact with the chip, and it sounds like they do, would opening the case up and applying thermal paste to the standoffs help?
Depends. Some of the stuff "came from China" is assembled by low paid labor that barely cares that all the parts make it into the case. If you watch Big Clive tear apart dodgy bits of eBay cruft, wires get reversed, quality control may be at a minimum, etc. It is very similar with some of the more technically sophisticated gear ... poor design, lack of thermal paste, too much thermal paste, poor coupling between a component and aluminum extrusion, etc. So much can go wrong and lots of it is "inherent by design". Skepticism is good.
Also, do you have any experience with Thunderbolt bridging between TN and non-TN devices? Is it supported?
I do not, I am sorry. I do a lot of hardware work but I do relatively little with Thunderbolt.