The first few batches of Athlon IIx4/x3 CPUs were not propus but were instead denebs with disabled L3 cache. Newer propus chips do not have L3 because they are not made from the same deneb.
The X3's are the salvage yard for dysfunctional cpu's. Open cpu-z and check for the "revision" on the cpu tab. The 445's are the newer C3 stepping as of 5-10-2010 made from Propus C3 640 or C3 Deneb cores. So OP has a locked up C3 PhenomII.
AMD is going to continue salvaging it's dysfunctional 4 cores and use them as x3's, if demand becomes so great they may lock up some healthy X4's to meet demands.
If I were going roll the dice on a X3 today I would buy a 445 and if the fourth core was bad I still would have a solid C3 X3 to overclock.