The Venus 12 is also a pretty good heatsink/fan for AMD 64s from what I have read.
The difference between 754 and 939 sockets isn't much, the 939s are more expensive I will admit, but they generally perform better than the 754. Also, AMD has basically decided that the 939 socket 64 bit proccesors are the right way to go, and they have pretty much stopped manufacturing 754 and 940 socket proccesors, so if you get a 754 socket motherboard, it won't support any newer 64 bit proccesors if you ever wish to upgrade.