Not that they aren't good, its that you do not use 6 cores.
To put things in perspective for you here, you are better off with less cores at a higher clock speed than more cores at a lower clock speed for gaming.
Look into the 955 black edition, I believe its clock speed is somewhere around 3.4 ghz.
I would also strongly reccommend that you take a look into a core i5/p55 build, as you will spend about the same amount of money and end up with an overall faster system. The i5 750 is faster than all but maybe one of the phenoms, and is only $199, plus the p55 motherboards are about the same cost as the AM3 boards, if not cheaper.