Admittedly, I don't have any experience with the Venus 12, but I'm a big fan of the Zalman heatsinks. I recommend you just go for the CNPS7000A-AlCu instead of the copper version, though. Same performance, lighter weight and lower cost, even if price isn't an issue.
Probably the best heatsink you can buy, though, is one of the high end Thermalright ones. Sorry, I don't remember the model, but it's made specifically for the Athlon 64, I think. They give very high cooling performance when coupled with a good fan.