I just bought an EVGA GTX 580 card,
I am thinking about liquid cooling...but I am not sure
I know next year I will get another 580 for SLI, but for the moment does the 580 need liquid cooling???
Nope, it does not need liquid cooling. But that depends, what case are you using? What are the highest temp's your GPU is hitting? I believe that as long as your GPU is at 37-40 on idle and 80-83 under load, you should be fine. According the nVidia's website, the max temp for the 580 is 97.
That is a great point. The GTX580 runs cooler and should not have much impact on your overall case temperatures. Liquid cooling would be used if a) you are trying to set a personal record with overclocking, or b) you just can't stand any fan noise whatsoever. If that is the case, you already have liquid cooling throughout your rig, and already know the answer to your question.