Phenom II X2 550 is unlockableeither on the chiper boards as well as expensive mobo.
I'll post model names:
Gigabyte GA-MA770-UD3 rev 2.0
Gigabyte GA-M720-US3 (jes, nForce ulocking PhII well as SB750 )
Gigabyte GA-MA770T-UD3P (AM3 board with DDR3 DIMM Slots)

All of those 3 boards are cheap and You can unlock your PhII X3 or PhII X2...