I would get a dual-band wireless-N card. These tend to run around $30, but in my experience are a lot faster and a lot more reliable than the cheap $15 cards or USB dongles.
Edit: I am currently using a Netgear dual-band router, which has been flawless. The wireless card I sometimes use (I'm using PL in that room now) is a TP-Link. Since Linksys has been bought by Belkin, I would no longer trust them to be reliable. My old D-Link router was reliable for many years though.