Do you have an AMD64 chip (x86_64) or a pure 64bit chip - like the itanium. I think you probably have an AMD64 unless you are running a server. For this chip you could use the standard x86 binaries, as the AMD64 supports 32bit natively. However this will negate most of the benefits of having a 64bit chip. I've never used debian so i can't tell you exactly what you need, but get the ones with AMD64 or x86_64 in the name.
Hope that helps