Xeno, Do u know the difference between the Phenom II and Athlon II processors Architecture wise? They are having the same architecture, Athlon II is just missing the L3 cache. But in lot of case by using M/B with south-bridge SB710(AMD 790, 785, 770 Chip-set based boards), people were able to unlock the extra cores or L3 cache.
Athlon II X4 620/630 are nothing but some Phenom II processors with faulty L3 cache that has been disabled. In 1st batch of these processors, a lot of people successfully unlocked the cache and they become fully working Phenom II processors. In newer batches, AMD removes the L3 cache physically.
So believe me, Athon II X4 is nothing but a Phenom II without L3 cache.
My recommendation for 785 chipset base M/B because of the fact of Good inbuilt Graphics core 4200 which is far better than the 3300 Graphics core present in 790 chipset based boards.