You can only unlock the extra one/two cores on the Phenom II X2/X3 sometimes, if the disabled core(s) is/are not defective, and trying to unlock them can cause system instability, if the cores are defective. To unlock extra cores you need to have a motherboard which has the AMD southbridge SB710 or SB750 which supports ACC. Or, you can unlock cores with the 'Core Unlocker' feature on the ASUS 890GX motherboards.
If you actually want a quad core though, you should get a Phenom II X4, but there is a relatively good chance that the Phenom II X2 or Phenom II X3 will unlock into a quad core though.
thanks for the advice