As said above, they haven't been offically announced. Even leaked information could be changed last minute by AMD. And the information on various sites tend to be drastically different.
Extreme 1: AMD said that Hammer will be released at 3400+ speeds. Some assumptions about efficiency means that 3400+ would be roughly 2.0 GHz. Then assuming that Opteron and the Athlon 64 would be the same speeds at release, then the Opteron will be released at 2.0 GHz. Thus it would be quite natural for AMD to brag about their fastest processor and not the rest, it makes sense for AMD to release the Opteron at 1.6, 1.8, and 2.0 GHz.
Extreme 2: AMD said Opteron will be released at 1.6 GHz. This tends to be much more believable than all the assumptions listed above (however AMD could always change their minds). Again using the argument that it would be silly for AMD to annouce their slowest Opteron, 1.6 GHz must be the top Opteron speed at release. Thus the three model numbers could mean 1.2, 1.4, and 1.6 GHz or they could mean 1.4, 1.5, and 1.6 GHz.
Andreasl posted a batch of numbers right in the middle of the extremes. I haven't seen that on any site, but it makes an interesting compromise. I tend to believe the 1.4, 1.5, 1.6 group - but I'm just guessing like everyone else.
Eight days and we will know for sure. I'm quite interested in the reviews, but I believe that Opteron will initially be a flop - it won't shine for another two years.