Get the Linksys (Cisco) BEFSR41 version 3. Its new, its cheap, and it works great. I'm staring at mine right now, with its little winking lights. Also, for this unit you don't necessarily need to go the ebay route. Many online/offline stores carry this thing for CHEAP, look around. I typically avoid retail like the plague, and I bought it at Best Buy for like 40 bucks new.
Oh! In case you buy an older one - the older (not ver.3) model of this also works great, BUT make sure you download the updated firmware BEFORE hooking it up. That way if it doesn't like something about your setup (my cable provider told me the stock firmware on a lot of them doesn't play well with some of the modems), you have the firmware on your computer and can flash it without having to change anything. Actually, you might want to flash it anyway, I know for example the newer firmware is "Xbox compatible" so it probably performs better. My friend has the older version, and this seemed to hold true for him.