It depends on what you call "basic" overclocking. I would say your best bet of getting that speed with a significantly cheaper processor is with one of a few particular Opteron 146 or 148 batches, but that involves a fairly large overclock percentage-wise, and you can only get a guaranteed batch number if you order off ebay (like I did) or buy at a retail store (where you can see the numbers on the CPUs through the boxes). There are some 3200s, 3700s and 4000s that can hit the speed, but it's not that common with those.
As for the batch codes, I did a fair bit of research on them last week and this seems to be the trend on 146s on good air cooling, although the other Opteron models with the same codes should perform similarly:
CABNE 0528GPMW : the absolute best, rebadged FX57s, can hit 3ghz on stock voltage and usually about 3.2ghz maximum (almost impossible to find now)
CABYE 0540FPBW and any other CABNE except for CABNE 0540s : still very good, about 2.8-2.9ghz on stock volts and max out at 3.0-3.1ghz
CABYE 0540FPAW and CABYE 0540FPMW : max out at about the same levels as above, but require a bit more voltage; I got an FPAW
any CABGE : not that good relatively speaking, only get to about 2.4 on stock voltage and 2.7 maximum, these are known as cabbages

any CAB2E : quite variable, can be as good as any of the above, rather hit or miss
If you don't want to bother with that, 2.6ghz (FX55 speed) is probably a more realistic target, which can generally be achieved by even the crappier Opteron batches and most normal A64s. In general, the Opterons on average seem to overclock better than A64s. Note that all the Opterons have 1MB of cache, so they equal the FXs in that respect, but out of the 939-pin A64s, only the 3700 and 4000 have that.
Also, one thing to keep in mind the older Asus nforce4 boards are all mediocre HT overclockers. The new A8N32 board should in theory be very good with the 8-phase power regulation, but not too many people have it yet and there isn't a whole lot of information on how well it does.