Sennheiser HD497 is a good choice, low imendance - good for sound cards, no need for amp, should have good bass and best sound balance of all the 4x7 series. And first of all they're CHEAP!

and easy to get. Be sure to check them out.
Here I found you a link with a short review of the headphone. And if you look aroung there are many other suggestions in the buying guide. There are newer Sennheiser portable not full size headphones - PX100/200, also good for computers.
Oh and HD570 are quite different than HD580 - which are more like the top of the line HD600, HD570 is more like HD590.