hello..
pls. see the factors which are need to checked to get max from your DSL.

1.Line
see : SNR value (higher the better),attenuation (low),CRC (means having loss)
2.MTU ( Max transfer Unit ..1500/1492),windows receive size.

Make sure about these setting and see the difference ...i recommend..pls be careful about WRS and MTU ...if you are using windows XP you dont need to change it ..