Hey, all the features you want have standard packages for OpenWRT...
Asterisk - well that's a complex application, if you're asking for it you probably know how to configure it, otherwise some good info here and on the web...
IPSEC - Ports for OpenSwan and kernel modules to be a client and server...
DynDNS - X-WRT (http://www.x-wrt.org)'s webif^2 interface lets you configure this (once you've installed ez-ipupdate, it's a link so easy to install)...
Qos - Again, X-WRT supports this out the box (once you've installed qos-scripts, same installation ease)...
All the packages installations are fairly simply done, either by command line or from the web interface. Suggest looking into X-WRT for a good set of management tools over and above what you've asked about...
Hey hey!! 