A router with QoS is a must, and it must be properly configured
Really, a must, definately, positively, most desireably, a must.
My personal experiences with consumer grade routers is that the cheapo ones fail, really across several brands, and the nicer models generally run along just fine. I've been putting DLink DIR330's in remote locations because its got a fairly large amount of memory and a fast processor for something that can be had around $100 "consumer grade VPN router". The VPN part is a nice option to have if needed in the future.
For main locations I want more than just a router with NAT and a basic firewall, but not a big price tag.
My experiences so far:
Untangle - Great in every regard except SIP. Just had bad call quality with it.
IPCop - Liked it, for some reason, 3cx didn't. Something about "symetric NAT" vs "full cone" and I couldn't get the built in proxy to work correctly with the remote locations.
Smoothwall - seemed lacking in features out of the box.
Endian - So far so good, NOT using the SIP proxy (that caused problems) AM using the spam filtering.
Going to be trying "Astaro" as it seems to specifically support SIP SERVER behind it, and load balancing.