If you have a small number of wireless devices in your household as well as your neighbors then you can get by with the single band 2.4GHz wireless adapter. If you have a congested network map on the 2.4GHz frequency then it's best to pick up the dual band adapter and run off the 5GHz frequency. Can you please state what the wireless adapter on your laptop is?
I would like to stress though that if placing a PCI-E based Wireless adapter in your chassis then it's quite possible that the antenna's will have to pick up the signal through a lot of material/devices thus affecting your wireless performance/computing. I'd advise in picking up a wireless USB driven adapter and have it placed on your table top or the front panel ports. Another option would be to pick up some larger antennas or antenna's with some wired extensions, like this
There no mention of the dual band wireless adapters model but I'm going to assume that it's also going to go on an expansion slot on the motherboard.