DD-WRT is awesome for that. Ill never buy another router that doesnt support it. I just wish I had the money for a rackmount router
It doesn't have to be rackmount.
Just use an old PC.
The steaming turd my ISP provided to me dropped like a little girl when I was getting DDoS'd by some stupid child because I upset him.
I installed pfSense on an old PC and he was no longer a problem