@Ranmaniac,

Based on your link rate, then the client device speed would be average, if not above what should be expected.  It is typical to see only 30-60% of the throughput offered by your link rate.

Do you know that your powerline devices are on the same circuit? If the data has to travel through your breaker, your signal will be drastically affected in terms of both latency and throughput due to the distance the data must travel on your powerlines.

As this is the expected performance for your link rate, I think your best bet is simply to test if the link rate improves when you move the adapters around your home, or remove devices from your powerlines. You may be surprised at what devices can cause interference.

Unfortunately, upgrading to a higher powerline rating is not an option if you want to use the adapters you already have. (All Powerline adapters in a network will adopt the maximum speed of the slowest adapter)

If you are looking to use the connection for higher-bandwidth applications, then you might consider looking at a mesh solution, as they do not suffer the same performance falloff seen with Powerline and Range Extenders but allow a strong wireless backhaul to be established between mesh nodes.