The HD600 series really isn't that hard to drive. I think headfi has drilled into peoples heads that you need a power plant to drive everything. I find them rather easy to drive. You will loose some fullness with a standard laptop output but it doesn't sound terrible.
i agree, i have some hd600's and they are really not difficult to drive. sure they will sound better with a headphone amp but they do not need huge amounts of power.