nope. the 640gtx is not an entry level GAMING gpu. the 650 gtx, or HD 7750 is. use that as your baseline for entry level graphics cards. also, that h61 chipset won't support your ivy bridge i3 out of the box, so you might have issues getting the machine working. make sure the manufacturer/merchant updates the bios to support that i3.
really. and sorry for the stupid questions still a newbie what do u mean wont suport ivy bridge?...thanks
sure... the core i cpus are separated into different generations.
Nehalam - 1st gen ~ socket 1156
Sandy Bridge - 2nd gen ~ socket 1155
Ivy Bridge - 3rd gen ~ socket 1155
Haswell - 4th gen ~ socket 1150
as you can see sandy bridge and ivy bridge cpus share the same socket, which means in theory their chips will in the same motherboards. however, ivybridge came with certain architecture changes that required a new "chipset", the sandybridge LGA 1155 motherboards had a chipset with a 60 in the number. like your chosen motherboard is a H61, which means it's made for sandybridge cpus. The ivybridge LGA 1155 motherboards all have a 70 in their chipset number... all the ivybridge motherboards will work with both sandybridge cpus and ivybridge cpus out of the box. but since ivybridge came later most sandybridge motherboards WONT work with ivybridge cpus out of the box.
I know your cpu is an ivybridge because of the 4 digit number on the back of it. sandybridge i3s all have a number in the 2000s... so a i3-2120 would be sandybridge, where as all ivybridge i3s will have a number in the 3000s... like your i3-3240
so, in your case, either get an LGA 1155 motherboard with a chipset sporting a 70 in the number, or get an i3 with a 2xxx number, or make sure the distributor/merchant/store updated the bios of that motherboard to support your cpu before they send it to you.