IMHO...
the two best solutions for Gigabit Ethernet on RH / Centos Kernels (SME) are
e1000
tg3Both work Gigabit "out of the box" (are in the kernel).
e1000 is the driver for
Intel Chipsets used by Intel, Super Micro,hp, Dell Optiplex &PowerEdge
the Chipno/-labels are: 82540 or 82541 or 82573
there are Dual and Quadsolutions for pci and pcie which contain 2 or 4 independent chips "on board"
both then work with the same driver and give independent ports (Quad isn't that useful for SME

)
tg3 is the driver for
Broadcom Corporation pci,pcie chips (Delll Poweredge, IBM eserver, hp servers)
chipNo./-labels ar BCM5721 or BCM5751 or NetXtreme
I have seen Dual boards advertised - they should work and give you 2 ports for SME
...my personal experience with those two are flawless.
Regards
Reinhold