Agree, the locked multiplier doesn't matter, because you just up the FSB.
The key to OCing is having the correct memory. Right now, many are having good luck with OCZ Platinum EL, or Gskill.
On the MB, many go with the MSI Neo2 Platinum. Some screw up and then send the board back, but that's mostly human error. The reason many go with the MSI board, is because you can up the memory voltage to 2.9 or above. On the Asus A8V, the most is 2.8, which is fine for most, but for extreme OCing, many go up to 3.2v or so.
Go for the highest chip speed you can afford, because they all OC by at least 10%.
Here's a chart to read.
http://www.c627627.com/AMD/Athlon64/
Go for a 3800, a 4000, or an FX53 if you can afford it.
Once the FX57 comes out next year, I'll be selling my FX53.