reply to Manta
Re: [H/W] H/W Performance advice please...? OK, I managed to get hold of an 1841 and adapted the config from the 881 (interface names changed etc) and ran a speed test. Was a bit disappointed to only get 20Mbps this time....although not massively shocked, admittedly.
Have been turning off some features to see if I can coax some more speed from it. A few such as 'ip flow ingress' and turning off an outbound ACL may have improved it a smidge but it could well have been just the error margin of an online speed test. However, turning off 'ip inspect name internet-cbac http alert on' brought it up to 34Mbps and I don't think I'm using any features that would require http inspection anyway.
The UC540 manages 22.5Mbps or 28Mbps with lower CPU after the same mods.
I was looking at the possibility of an ASA5505 as that ought to be able to firewall, NAT, 3DES and QoS. It won't do GRE but I could have the ASA do 3DES and the UC540W do the GRE tunnels. Anyone see any pitfalls or oversights in that?