Recommendations for headphones under $400?

I would agree with noble100.  I've bought several headphones from Massdrop over the years.  IMO, I think the best deal (price/performance) on the headphone market is the Massdrop Sennheiser  HD6XX, which is the exactly the same model as the Sennheiser HD650.  You'll need a decent headphone amp to properly drive these headphones, but once broken in, they are an excellent value.  I'm not sure what model you have, but my Grado GH1 w/ G Cups were very comfortable and the bass was very good.  You may also want to look up the Grado line, especially if like their sound signature.  Good Luck!

I did buy a pair of the hifiman h400i and am awaiting delivery
Hopefully this will do the job!

If you aren't blown away I'll eat the box!Well maybe I would send you a nice little tube amp to try before eating said box!Congrats,
 Give them a good running in and let us know what you think..

So now I have a new problem that makes me think I must be missing something but if there are any Hegel H300 owners here maybe they can chime in.
I am now using a Hegel H300 integrated for my system and this does not have a headphone socket.
No problem I thought I will just connect a headphone amp to the pre outs of this amp.
However Hegel appear to have designed this unit so that when you mute the music through the speakers it also mutes the output to the pre outs.
This sort of defeats the object of my usage unless anybody knows a way around this.
I have emailed Hegel themselves but as of yet still awaiting their reply.

Hi uberwaltz,

     I'd be very interested in Hegel's rationale for not including a high quality and convenient method of connecting headphones to their top of the line $5,000 integrated amp while the vast majority of their competitors do so, often at a fraction of the Hegel H300's price.  WTF?

     It's commonly known that extreme cold slows down cognitive functioning.  I apparently incorrectly assumed the execs at this Norwegian company would be making these critical decisions indoors with the heat on.
     Did you know it had no headphone accomodations when you bought it?  On an integrated amp, that would be a deal breaker for me and likely many others.  
     
     If you don't want to sell your H300 and buy a more headphone friendly integrated, the only solution I'm aware of is buying an external headphone amp/dac with a digital input, se or xlr analog outputs and a headphone jack.  
     The procedure for hooking up an external dac is detailed in your H300 owners manual.  It basically calls for connecting the H300's digital output to the external amp/dac in what Hegel calls a DAC-loop. I learned of this on the linked thread here:
  
https://forum.audiogon.com/discussions/adding-a-dac

Tim