Well, I went out and got a Gigabyte GA-945PL-S3. Seems to be working fine, but experiencing severe problems getting the onboard NIC going with the official RealTek R1000.5.tgz driver... The NIC sometimes "disappears" randomly, as if there is some kind of driver issue. This happens every few minutes. I've managed to mitigate the problem by doing the following:
echo 98886080 > /proc/sys/net/core/wmem_max
echo 98886080 > /proc/sys/net/core/rmem_max
echo 98886080 > /proc/sys/net/core/wmem_default
echo 98886080 > /proc/sys/net/core/rmem_default
echo 0 > /proc/sys/net/ipv4/tcp_timestamps
echo 1 > /proc/sys/net/ipv4/tcp_sack
echo 1 > /proc/sys/net/ipv4/tcp_window_scaling
but the NIC still seems to "fail" from time to time, not sending or receiving any packets off my LAN. The above just extends the time between failures.
All in all, not such a bad board, but has definite issues with the NIC and the manufacturer's Linux drivers under FC6.