so why did u have to pay for DDWRT?? lolz
I use the free one and it has QoS.
as for your question.
Under Netmask Priority - u put the IP address or a range of IPs that you want to set Priority on.
The MAC priority is similar, only u put each device's MAC address on there, can't put a range.
What I use is MAC priority and added the PCs or device that will be Exempt.
So I added my Tmobile @Home router to it, and my Server. (not that voip takes up so much BW, but I want it to have clear voice while im downloading my pr0ns at full speed)
For this to work, you need to set the uplink and downlink speeds (probably the lowest that you want)
Now, since you have the Special Edition, it has a Per User Bandwith Control feature. That's probably on a different page than QoS.