the A64's have a locked multi for going up but you can go down. The reason for that is because of the Cool n Quiet Tech. If you enable it, during idle the cpu will go to 800mhz and lower the voltage to run silent and cool. Thats why the multi is unlocked going down.
The Athlon FX's are fully unlocked but thier expensive.
The S754 is Single channle DDR, the S939 is Duel channle DDR. Not like the duel channle on the AXPS' where you gain 100 points in sandra.
This duel channle actually doubles the memory bandwidth. The bandwidth increase as for right now doesnt help much over single channle performance wise tho.
For the 10 Multi youre ganna have to buy the 3000+ Newcastle. Or the 3200+ Clawhammer