I just grabbed a standard set off of Amazon, which at the time happened to be these. Don't pay 70 bucks for those though; I'm sure there are better and cheaper options available.

I'm curious why your experience with these would make you think they don't have the bandwidth for the Steam Link. I think the Link caps its bandwidth at 30Mbps (or it used to, anyway) and even the most basic powerline adapters on Amazon right now are 200Mbps. Even with the shitty old wiring in my apartment, I have very little problem maintaining the necessary speeds. Like I said, I get stutters every once in a while but it's extremely minor.

(This isn't a dig, I'm genuinely curious -- I have pretty much no experience with these, and just grabbed a set off of Amazon and had no problems with them. I'm interested to hear what your take on them is since you've tested a bunch.)