How to accelerate Sify Broadband 256 kbps conn

Well I have just renewed my Sify BB connection with the new 1 GB 256 kbps pack. Now the prom is that if i use any download manager wwhich downloads using multiple connections(threads) like DAP, it gives me speed in excess of 256 kbps but when i download directly or browse or even view videos in Windows Media Player or Winamp....the speed keeps on fluctuating and no way i get a constant 256 kbps but rather an average of about 80-100 kbps......as a result i am not able to view any video or listen to audio....and it keeps bufferingSo my point is that since download accelerators do fetch me speed of around 256 kbps easily, it means the bandwidth is available to me So is there any option that can help me get full potential of my alloted 256 kbps bandwidth while browsing, playing vidos etc ??In short , I wanna know if anybody knows of a good internet accelerator program( and not a download accelerator program)Thanks