As long as its an N rated card, prefereably with MIMO and multiple antennas, then it will give you good speed. G rated cards are older and slower, mimo cards (multiple antennas) have multiple signals, can be dual band, and if linked with MIMO routers give faster and better quality signals.
While I agree this is normally the case, I actually struggle with N in my house. Router is the other end of the house (using an apple timecapsule), my laptop a macbook pro with a wireless N card works brilliantly on G, Its not the strongest signal where I use it (about 60%), however switching to N my signal drops to around 23% and doesnt sustain a constant signal. If I move one room closer N dominates the G but for some reason my room doesnt like N signals.
As someone mentioned earlier, if you dont mind a bit extra on cost and are willing to use homeplugs, then this is deffinately the way to go, brilliant connection through them as its just a wired connection using the electrical cables in your home. The only thing to watch out for with the homeplugs is if you have a set of logitech Z5500 surround speakers. When my homeplugs are in I cannot use the speakers as the bass constantly pops.