I don't have personal experience with DL-655. But others at dslreports have not said anything bad about it.

For some of the QOS routers, just turning it on will be enough. The RTP packets are marked with a IP precedence 5 and they are automatically given high priority. On some routers, you would have to give priority by MAC address. In this case all packets coming out of that MAC will be given highest priority. On more expensive routers, you can match packets based on your own criteria and give those packets specific bandwidth.

Many users have good results with getting a simple G router and flashing it with Tomato/DDWRT. Some of good ones mentioned are Trendnet 631, ASUS 520GL, etc.. You can also get a better Netgear model and try it out. See if it works well during upload/download. Make sure you are able to return it without restocking fee if you want to just try some from retail stores.