new wireless cards for our dell laptops

Hi,

We have a Dell Studio 1558 running Windows 7 and a Dell Inspiron 15R 5520/5522 running Windows 8. Both of these laptops speed test very slow on our home WiFi, compared to the throughput we get on newer devices like our phones, as well as that shown by official testing done by Xfinity.

If possible we would like to install new wireless cards that will support 100mbps as well as cards that have a 2.4 and 5.0 Gigahertz setting. Of course we want these cards to have available drivers for the above two machines.

Any suggestions are appreciated.

Thanks