You are right, your 1711 give only 10Mbit/s on it's 100Mbit
interface, it depends only on hardware, in fact with the main processor and the ability to switch packet. I tested some router and this is my personnal (very personnal) benchmark with 2 100Mbit/s inferfaces on a router and multiple test like FTP and ping.
Nortel ARN => score = 10Mbit/s
Nortel ASN => score = 20Mbit/s
Nortel BCN => score = 40Mbit/s
Cisco 2621 => score = 30Mbit/s
Cisco 7536 => score = 85Mbit/s
I think you cisco 1711 is similar to ARN (low price router)
with same generation of procesor. Routing packet is very expencive in term of procesor time. If you want more speed change to my favorite router, the cisco 2621, not too expencive and fast enouth, but don't expect 100Mbit execpt onto a switch !