Sound card, USB DAC, or Headphone?

[ShadowDrifter]

I'm hoping that I'm in a right place for this topic.
All right, I have researched to get a better sound quality but haven't able to get an answer that i'm looking for. Should I upgrade a sound card, usb dac, or headset.
My current set up is SB Recon3D PCIe with PreSonus HP4 Headphone Amp.
Klipsch ProMedia 5.1 is connected to sound card and HP4 amp is connected to headphone out line from the sound card.
I have a Shure SRH 1540, Philips Fidelio X1/28 (switched the audio cable), Beyerdynamic MMX 300, Sennheiser PC 360 are attached to HP4 amp. I also have various NC headphone from Sennheiser to Bose.
I ended up having well over 20 headphones. My family thinks that i'm an audiophile but I believe I'm far off from it. But I do enjoy a good sounded music.
I bought a Fiio E17 USB DAC, Audioquest Dragonfly v1.2 USB DAC to attempted to improve audio quality but I'm just not happy with them. These aren't any better than SB Recon 3D with HP4 amp.
I researched high and low for seeking a better audio quality but I have failed to achieve that.
So here I am to ask pros' opinion.
Which would be a better upgrade: a sound card, usb dac, or a headphone for my situation.
Current budget would be $500 but could be more. It really depends how much of upgrade would it be for audio quality.
Also I found out that sample rate and bitrate are important as well.
Most of audio that I listen to has sample rate of 44.1 khz and 320 kbps. Or 48 with 320.
I just want to create a better audio for music that I listen to. Don't care too much about gaming sound but already got three gaming headsets, PC360 MMX 300, and Astro A50.
Thank you for your time for reading and attempting to understand my request when many grammar and spelling errors occurred.

 

[rahul_muzik]

I suggest you to buy an external DAC & provide digital input via sound card coz i see that your sound card has optical out & it will sound good since the DAC is powered externally & do not suffer much of the interference which sound card generally encounter . I have an M2Tech evo dac for sale which sounds extremely fine but i'm looking to upgrade to hi end in the range of 2L, so considering to sell it. If you want to buy then PM me.Just my idea,didn't mean to push you to buy mine.

 

[Hari Iyer]

IMO upgrading the headset will be a better option as you tend to get adapted to the sound signature of the headset very much faster as its very close to your ears and is isolated from the room. Even the new upgrade will be able to satisfy your listening for a some listens after your ears get adapted to them too.

Its much better to move to speakers if space / hardware permits as the adaptability of the speakers to the ears is quite long before you begin your next upgrade due to the external environment.