You may find, the paper I attached on my OP, a better guide to selecting a router based on its performance.
The older reference sheet, that Leo provided, has, for example, the 1941's Kpps as 299, and it translates this as 153.08 Mbps (as defined at the top of the document). Also note, this PPS rate is for minimal size (Ethernet) packets.
The later whitepaper, in table 1, lists the 1941's Kpps as 330. This too, going by RFC 2544, uses (Ethernet) minimal packet size. However, that same table shows maximum Mbps as 2,932 for a 1941. This though, is for 1500 byte packet sizes. This shows packet sizes greatly impact the bandwidth throughput of the router.
As to encryption performance, table 2 show that, and for a 1941, 170 Mbps is listed. Cisco doesn't mention for what packet size, but if also for 1500 byte packets, encryption reduces bandwidth throughput to 5.8% (170 / 2932)!
The whitepaper's other tables, and text, explain other usages and how they impact throughput.
At the end of the whitepaper, Cisco provides a bandwidth capacity recommendation for many ISRs (figure 1). For the 1941, Cisco recommends it for 25 Mbps of "WAN" bandwidth. ("WAN" really meaning full duplex, or 50 Mbps of aggregate transit bandwidth.)
This Cisco recommendation is very conservative, it usually insures it's unlikely you'll run into capacity problem regardless of your configuration and traffic, if you don't exceed the recommendation. But you can often use a "smaller" router than Cisco recommends, if it's not subjected to all the possible situations that lead to Cisco's bandwidth recommendation.
BTW, before this kind of Cisco whitepaper, I use to take the older performance sheet's bandwidth number, divide it by four, to provide a rough ideal of what a particular router was suitable for. Doing that, for a 1941, I get about 38 Mbps, not that far from Cisco's (again very conservative) recommendation of 25 Mbps.
