I bought a Macbook Pro last July, so it's not the latest model, it's the Penryn one. I was thinking about buying a new pair of headphones, but I don't want to spend a lot of money in headphones that are too good for the Macbook Pro. So assume that I'll be listening to CDs, no mp3s, headphones plugged directly to the computer. Is a Sennheiser HD555 or HD595 too good? Will there be a difference compared with a less expensive pair of headphones? If so, what's the best I can have without having to sell a kidney to pay for it?