I am going to purchase either the Grado SR80i or SR225i. I've decided that they fit my preference of rock music well. I, however, don't know if it is worth it to buy the SR225i. I've never owned any good headphones before so I don't know if I'll be able to tell the difference between the two. I also want to buy an amp.Do you think an amp is necessary for either? Can I get some suggestions? In addition, are the cushions that they come with are sufficient or should I invest in different ones. I am willing to spend about $80, give or take a few dollars, if I buy the SR80i. However, I want to only spend about $50 if i purchase the SR225is. If you think it is absolutely necessary I willl spend more money on an amp. Thank you.