Update:

Tried Crossover Cable - Replication still extreme slow.
Changed Mirror Interface (both Sides) to old INTEL Pro 100 - Replication only 40 - 60 KB/Sec.
Build a loadbalance/rr bond with two Broadcom Gigabit NIC's and used this for Replication.
Still slow: 400 - 800 KB/Sec. Same with 802.3ad Bond (BTW: OPEN-E TCP Testprogram
reports 100 MB/SEC with this Configuration)