Yes that motherboard can unlock cores. But I wouldn't buy a 550 or 720 and 100% expect to be able to unlock the extra cores. If I were you I would go for the 720 so in case you cant unlock you still have 3 cores. I got my 720 last month and I was able to unlock it successfully with the MA770T-UD3P
I looked at the reviews for that mobo on Newegg and people were talking about how they were able to unlock the cores. Most major manufacturers came out with new bios' once it was learned that you could unlock the cores with ACC.