Do you already have your current computers hooked up to the router via copper cabling? If so, you just need to get the former device (or something quite like it). It will hook up to your current router and allow wireless devices to use it as a bridge to the network you've already got.

The latter device is the exact same thing as the CF or PCMCIA device you talk about except it attaches to the computer via USB. This is not what you want, unless you have a computer that you want to be wireless that has only USB ports for expansion.

Basically, you'd have everything set up as you have it now except the access point would be attached to the router instead of the laptop. The laptop would then be wirelessly attached to the access point. Think of it like a wireless extension cable. If you get more wireless devices, they'll all be able to use the same access point, too.