What do you plan on using the bike for? If its just normal street use you should go with the biggest size you fit comfortably on, which I am going to say is a 60. Have you ever rode a 60cm? If not I suggest you do.

Top tube length is key as members have said, but the other factors are just as important. If you ride a 58 now, I can't think of any reason to go smaller.

If you have stand over clearance for 60cm frames, you wont regret getting it especially if you plan on logging some miles on. Also different companies measure from different points so you may end up fitting on anything from a 58-62.