AMDZone has reviewed the recently announced Opteron 246 processor that runs at 2GHz coupled with a nForce 3 Pro board, they put it against a 3.2GHz Pentium 4.
This could probably give us a rough estimate on what to expect from Athlon 64 models to come, most especifically the 3200+ model which is said to run at the same 2GHz (and almost identical architecture & features)... perhaps chipset performance could represent some difference given the different target markets.
In a related note, The Inq reports that AMD will announce Athlon 64 as well as its official Logo on the 12th of August but at this time there won't be any benchmarks. We will have to wait until September 22nd for the official numbers to be released.