Sennheiser 600 vs 555 vs 595

Considering getting back into the headphone game. Previously had a Sennheiser 580 and Headroom Supreme setup. Did not get much use. With the baby coming and not able to play the stereo much, I am thinking about getting a pair of the newer Sennheiser. What do you think I should get?

Here is some info:
Source: lossless WMA files from computer and a Sony SCD-222ES SACD cd changer.
Amp: Headroom AirHead with Sony SCD-222ES. Not sure about computer yet.
Music: 60% Jazz, 10% Classical, 30% Rock/pop.
Habit: 75% on computer and 25% from CD player.
There were some very good deals not that long ago on the 600's. So good that it hardly paid to go to a lesser model like the 580.

Search the web and you may find some really good prices - especially just on or before major holidays.

If I don't use a headphone amp with 600, will it still as good as an unamped 555/595?
I sold my Senn 600s & replaced them with Grado RS1's that I really love: relaxing, not edgy, I have found myself listening for hours, way longer than planned. I use a Headroom Max amp. One warning: you must buy the Comfy pads (available from Headroom I believe) to replace the stock pads. With the comfy pads, the Grados are extremely comfotable, resting lightly on the ear, not around it; no sweat. I really swear by the RS1s. Get a nice mellow cable & a relaxing CD player & you won't want a speakerbased system.