It would DECREASE your ping probably by a bit.. 512 is around my upload speed, so I figure it'll depend mostly on the server.. I can ping anywhere from 15 on a NY cs server to 350 in Europe..
I'd say if your friend was hosting it or something, around 30-50
man i wish my cable company could upgrade my upload speed..... everytime my brother and i play cs with vent, the vent lags and the cs gets loss and lags too, sucks so bad, we got 128 upload speed, and if we pay 10 extra we only get like 100 extra kb download speed, we are at 14kb download speed, lol