Phenom II x2 555 with Gigabyte M61p-S3?

I have a am2 gigaybte m61p-s3 motherboard currently with a athlon 64 x2 6400+, it runs hot and stuff and i can get a phenom II x2 555 for like $40 with a after market cooler, and i checked on the gigabyte website and there is a bios update to take certain am3 cpus including phenom II quad cores and dual cores and ones with same tdp etc but the 555 says N/A, so would it not work or is it just an incomplete list?
 
its an old backup system that i paid like $50 for the board and cpu and threw old extra parts in and if i could get a phenom II in there it'd be better and its only $50 for the cpu and a ocz tower cooler and if the cpu doesnt take on the board i can throw the cooler and it wont run so hot