Youd need to find out your motherboard, as it may not support am3 processors.
if it does, the CPU choice comes down to what you want. the will be less effective for gaming at the moment, but more futureproof.
the 965 would be better in current games that use 2-4 cores, but would not last as long.
personally i'd get the 1055 and a decent air cooler, OC it can you are sorted.
but like i said, thats IF your mobo supports the proc.
EDIT: download this: http://www.cpuid.com/softwares/cpu-z.html
go to the mainboard tab and the model number there is the Mobo. google it to get CPU compatibility list.