Planing replace router with mikrotik routerboard.
40 users, all on wire, two lines, 20/20 and 10/5
Which routerboard i need?
How many RAM is enough, and how much CPU?

Deleted because not related.

40 users, all on wire, two lines, 20/20 and 10/5
Which routerboard i need?
How many RAM is enough, and how much CPU?

A friend of mine have similar setup with ~70 users, two ISP connections (20/20 and 8/8) and one L2L IPsec VPN tunnel (working over the 8/8 line). Three years ago there were only 20 users and they started with RB750. A month or two ago they substituted the old RB750 by RB2011LS-IN.

Currently (on RB2011LS-IN) memory consumption is nearly constant - 18-20 MB. During the periods when the users are active average CPU load varies from 24% to 57%. Previously (on RB750) memory consumption was the same, while CPU load was somewhat higher.

Hope this helps.

both 450g and 2011UAS could do the trick.
[40/26 Mbps even on small packets]

800/1200 quite redundant/OP IMO.
otherwise you should consider CCR, if you grow out of 450g/2011UAS.
800/1200 quite powerful routers, however, so if you can spend some more - its worth it.

p.s.
if most users are demanding[ie p2p and other stuff]both memory and CPU become critical :[

Yes, dhcp and dns proxy.
Some users p2p,maybe 5 max.
Vpn maybe 5max.

Yes, dhcp and dns proxy.
Some users p2p,maybe 5 max.
Vpn maybe 5max.

so, no insane pps amount ?
then even 2011UAS could be handy.
generally more connections/smaller packets - more memory/more CPU necessarily.
that's why i love upgradeable RAM options in some routers[just plug 8x bigger SO-DIMM module and you're in action again ! ;], despite minor impact on RB prices due that feat.
for sure - you can capture usual netflow from present router/network and can ask someone's with particular models - try to saturate their RB's with it. even handier - pick RB for testing[some dealers/shops quite friendly in that aspect, you even can do mild/primitive testing/benchmarking in offices, if bring you notebook with you.