I currently have V moda m100 over ear headphone and I wanted to replace it with something else.  I would like the new headphone to be under $300.  I'm looking at hifiman re400 and sennheiser momentum over ear headphones.  I may end up getting the momentum but would there be a big difference between this and m100?  I will probably use them for everything like home and gym.  
 
For the IEMs I've owned shure 215 IEMs and sold them but I wanted to get another pair... The iem that keeps popping up is vsonic gr07 bass edition.  I found some on ebay for $130.  What do you guys think?
 
Thanks!

You didn't specify what you were looking for, or what you didn't like about what you've tried so here a a link to Innerfidelity.  Take a look at the various sections of the wall of fame. That should get you a good idea of some of the better products in your price range.
 
http://www.innerfidelity.com/content/innerfidelitys-wall-fame