I have tried quite a few and find the Linksys/Cisco WAG120N and WAG320N to implement QoS very well.
Agree on a dedicated solution though.
I have my Cisco router hooked up to a Dell GX280 server running Kerio Control with 2 nics. Nic 1 to Cisco and nic 2 to internal 16 port gigabit switch which wires up the house.
Here too I tried quite a few of the open source solutions, but all of them lacking in features at the time of testing (3 years back). I settled on a commercial solution because it literally has everything I need and gives me 100% control over every device on my network.
I only have experience with MikroTik's QoS and it works pretty well for everything excepts game & voice, unless you have enough spare bandwidth to always dedicated for that purpose. Unfortunately QoS isn't something that is easy to setup on the MikroTik routers, unless you have lots of experience with it.
The Draytek units sounds pretty awesome, but they're very expensive.
I haven't played with QoS on those Cisco ADSL modems yet. The QoS on the D-Link and other entry level ADSL modems are usually incredibly difficult to understand and I doubt that they'll even work properly.