Buy a 5 Wood or a 3 Wood?

I have been gradually building up my golf bag. I bought the '07 Callaway Big Bertha 460 Driver and love it. I am thinking about getting either the 5 wood or 3 wood of the same series. I am not really what you would call a big hitter and I am a below average player. Any suggestions as to which club would be best suited for me? Thanks!