Can i use peavey 6505 combo amp to play green day, nirvana, Pixies, The Offspring, Rise against songs? Is it possible to get somewhat similar sound from that amp? I have an American Fender Strat
you can, but i think a british voiced amp would work better for what you want. Also, you might get more replies in the GG&A section :P
yup. but, as mentioned above, a brit voiced amp (marshall typically) might be a better starting point.

the 6505 combo is a little bit thin on lower gain settings. its not bad by any means, but you should definitely try one before you commit
a lot of people around here tend to like Blackstar amps. The ISF feature can change froma british voice to a more american voiced amp. I want to say maybe Jet City would be a good option but not totally sure on that one