If you'd like to try an alternative to the suggestion to that made by @ogiewon (that eBay price is good the seller is reliable, BTW):
Assuming that the WiFi plugs cannot be integrated directly into HE, you can still control them via HE if you use the Echo Speaks + Actions app.
While previous versions of ES were associated with hub slowdowns, I don't know if anyone has seen a HE slowdown with the most recent release.
