I did not see benchmarks on ethernet either; however, by the nature of how copper ethernet works a PHY is a PHY, it will always transmit at line rate (e.g. 2.5Gbps always). The only way to tune it is to change packet size, e.g. enable jumbo frames you will get more data through since there is less preamble/packet info transmitted, more raw data. These PHY's need to interoperate so they follow a strict standard and data rate with one acting as a master and the other as a slave to stay in sync. So there isn't too much point in benchmarking network cards. The thing about these cards though is since their data rates are higher there is less latency on the MAC layer since they have to operate faster in order to support the faster line rates. In a way it is overclocking the PHY to MAC layer with faster ethernet standards.