i got some speedtest results with different speeds settings at manual config:
100baseTX, half-duplex : DL = 43; UL = 14.6
100baseTX, full-duplex: DL 50; UL = 58/xx
1000baseT: DL = 117/118 ; UL = 58.9/59 , MTU- std 1500 and Jumbo 9000 yield same response.
so i guess, i can stick for this kext...