There are basicly two major things that effect lag:
1) internet conection
2) location
Since you said you have DSL, the problem may not lie in the connection. From experiance, players with DSL usually get 90-200 pings. However, some providers aren't as good as others, and you might have just drawn the short straw. If that's the case there is nothing you can do accept maybe look for another provider.
Your real problem probably lies in location. Try to find servers that are located near you. For example, someone who lives on the east coast often times pings a lot better on an east coast than a west coast server. The change can be in the hundreds. If you are trying to play overseas it can be even more.
You said your ping goes up into the thousands... is it always there or just spiking? If it is just spiking, you might want to try to play at a different time of day. This was a problem I used to have with my cable. During peak hours (7-9pm) the service would cut off and go back on for half-seconds, causing my ping to sky rocket.
I really doubt it could be in your settings, but it might be worth looking into. Consider costomizing your configs. If you've never really done that, you might just want to download some other players configs.
I hope something in there can help you!