the speed isnt all that matters, its mainly the location of the server. I had a 256KBps DSL Connection earlier, and i was able to play cs:source and all my other games online with pings less then 100. And when i got my 2.5MBps connection, it didnt really make much of a difference (besides how long it takes to download maps and stuff). SO id say that yout 512k dsl will be very good for gaming.