If you are able to wait, if March is your upgrade date, wait until the new ones come out in June. If you MUST have an update in March, go to the Apple refurb units. Same machine, same performance, same warranty, and a few bucks less.
There is a story on the updates, by coincidence, on the main page here. As expected, it's sketchy, but may give a slight hint at what is next. Fact is, whether you buy the current line or wait for the new ones, you can't go wrong. Unless you do extreme gaming or a heavy video editing workout, either will have plenty of power for you.