Most x6 phenoms u can still purchase new are usually a 1045t, so a higher clocked x4 like the 965 may be the better choice, unless u can overclock the cpu the x6 will be better for battlefield 3. My friend has a 945 x4 @3.0ghz and a 5850 and the cpu bottlenecks the gpu to where u can play ultra to where my 3.4ghz x6 could, so if u want to get the most of ur gpu either overclock or go for a higher clocked x4.
Tigerdirect usually has the x6 1045t and some times OEM or refurbed 1055t+ x6 and some of the other x4s that isnt a 965 but still including the 965 x4.
Newegg has the x4 970 which is only a 100mhz higher than the 965, so if u can get a 965 x4 for about $90 id get that, or a 1045t to overclock