What sort of numbers were you getting?
It appears that I somehow managed to install both 8125 and 8169 (on rc2), but I also built an image with a huge amount of packages. I'm not sure how the system behaves or which one wins in this case, but I've been happy with my performance; ping is low, bufferbloat results are great, and throughput is ~850 on my 1g connection. I'm using cake sqm, irqbalance, set the cpu frequencies to max, and updated 40-net-smp-affinity.
root@OpenWrt:~# opkg list | grep kmod-r8
kmod-r8101 - 6.6.63.1.039.00-r2 - Realtek RTL8101 PCI Fast Ethernet driver
kmod-r8125 - 6.6.63.9.014.01-r1 - Realtek RTL8125 PCI 2.5 Gigabit Ethernet driver
kmod-r8125-rss - 6.6.63.9.014.01-r1 - Realtek RTL8125 PCI 2.5 Gigabit Ethernet driver (RSS)
kmod-r8126 - 6.6.63.10.014.01-r1 - Realtek RTL8126 PCI 5 Gigabit Ethernet driver
kmod-r8126-rss - 6.6.63.10.014.01-r1 - Realtek RTL8126 PCI 5 Gigabit Ethernet driver (RSS)
kmod-r8168 - 6.6.63.8.054.00-r1 - Realtek RTL8168 PCI Gigabit Ethernet driver
kmod-r8169 - 6.6.63-r1 - Kernel modules for RealTek RTL-8169 PCI Gigabit Ethernet adapters
Here are results of a speedtest run for anyone interested:
Idle Latency: 7.87 ms (jitter: 1.84ms, low: 4.24ms, high: 7.96ms)
Download: 849.58 Mbps (data used: 435.5 MB)
7.37 ms (jitter: 1.77ms, low: 4.85ms, high: 23.52ms)
Upload: 850.92 Mbps (data used: 1.0 GB)
3.95 ms (jitter: 0.43ms, low: 3.29ms, high: 20.47ms)
Packet Loss: 0.0%
Edit: I just realized I ran the wrong opkg command. I only have kmod-r8125-rss installed.