hi
If i read your post properly you are putting loopback interface in place for the reachability of the device independent of any of the links is up and carrying the traffic.
one more approach for the same would be having multilink bundle configured over the physical links without running OSPF in your network.
you can have LFI too if you want that in place but if you want them to be independent better go with the static routes and CEF with per destination load sharing instead of per packet load sharing.
Per packet load sharing may affect your voice traffic coz of the rearranging of the packets in both the ends.
since you have got only 2 locations thats the reason i suggest static routes here in the first place..
if you are ok with OSPF then pls go ahead and implement the same in your network :-)
if you ask about QOS -- you can go for LLQ for Voice and normal assured forwarding for the different traffic patterns available or being passed out in the network.
also key in aboutthe kinda voip equipment planned in your network ? is it gonna be a fxo or fxs or any other external equipment ?
so that you can plan the qos policies accordingly which has to be configured in the router based on the marking capability of the voip equipment and to the equipment to which its connected.
regds
