Wireless Networking Problems

Here is a link with specs on building one CHEAP this way you can try is before you buy it, as you will be out less than $20 for both. Let us know if this works as there are other solutions (repeaters). http://www.oreillynet.com/cs/weblog/view/wlg/448

I am trying to set up a wireless network between my home computers to play lan games. I have a DLINK DI-824VUP+ which has a small inbuilt antenna. I am trying to network with a computer downstairs but the floor is 8inch thick concrete and I cant get a signal. The guys at Computers Online are suggesting I use two directional antennas but before I buy them I want to know if they will actually work. Can anyone tell me from experience if this is going to solve my problem?