Hello! I'm going to buy new headphones and I need some advice. I have Koss R90 and the new headphones should sound better. I want to spend $300-400. I have a few questions:
1) I think I will buy 2 pair of headphones: canalphones (portable) and circumaural (for home use). Does it makes sense? I think that large circumaural would sound better, then canalphones. Am I wrong?
2) Which circumaural headphones ($300-400) and canalphones can you recommend?

I have read that in-ear "KOSS The PLUG", "KOSS SPARK PLUG" are good, but I think the price is too low ($10) for good headphones.
I have read that Sennheiser HD650 ($300) are good, but maybe HD650 are too good for human ears?

Thanks.

It depends on taste more than price. Some people like Sennheiser, some people AKG, some people like Grado, some people like Beyerdynamic, etc.
In ear headphones: consider etymotic, shure, ultimate ears.