In your experience, in what way does the DCA Aeon RT closed improve upon the K371?Fostex t-series lack lower bass, often there is a substantial channel imbalance between the drivers. They have rolled of upper treble.
Fortunately they are highly modifiable and react well to EQ. Once EQ'ed they sound great.
I think @Dan Clark made a wise decision to develop his own drivers instead of continuing to use the Fostex drivers/headphones.
Dan turned them into something 'better' (so did other companies) but there is so only much that can be done with physical mods.
The list I gave is incomplete. It's just what I hung onto. Didn't hang on to DT770 despite owning them twice.
To me it has a resonant and 'one-note' bass while others never hear(d) that. The treble peak needs some attention as well.
For the money it is a good headphone, the prof versions are sturdy as hell. The pads are well... need some attention now and then.
When it comes to cheaper good sounding closed headphones K371 and DT770 are about it.
Also the Takstar Pro82 is not a bad choice as well as the M50X and with some EQ the HD280Pro
There are probably some more but have no experience with those.
I own the K371 and I'm considering an upgrade. (I'm not 100% glued to the Harman target regarding tonality, but the headphones need to sound "balanced") Value is a bit personal so I'm trying to decide if they are worth it for me.