I'm looking at the Grado SR80 (£85) vs the Sennheiser HD580 (£85) or HD590 (£95). I'm planing on using these most of the time with my computer system at night, pluged into my Videologic Sirocco Crossfire amp. I might use it with my Marantz SR7300 receiver too, and also with portable players. So 1st, given the price what do you guys think I should go for? 2nd, I've read a lot about these headphones sounding much better when connected to headphone amps, how will my two main sources (sirocco amp and marantz receiver) perform in this regard?