Tried and true recommendations: headphones, amp, source

@freediver  

not true.

^^^Your ignorance shows if you don’t know HeadAmp..As for Utopia being garbage that may be true ONLY for your hearing/brain/tonal preference..I myself simply don’t care for the presentation of ANY transducer with metal drivers,some don’t hear them the way I do...
 Now back on track.
 New HiFiMan HE6SE from Adorama came in & are getting some run in time on an old am/fm radio while I wait until tomorrow for a new Pre/Head Amp/DAC(Audio GD "R28" R t R)to arrive..This thing is a MONSTER with 9.5watts,which should really bring the 50ohm/83.5db.HiFiMan to life...

OP"I just bought a pair of HifiMan Sundara phones to try out, and since they're middle of the road I can start there and determine if they are "good enough" or if I want to try something upwards from there.
I'm also going to start building the DAC/Amp side of things and I think I'm starting to understand it"....
 First:head-fi.org...
 Second the Sundara are a SUPERB value & a true benchmark of neutrality under $1000.00!
 As for tube amps,with Planar Magnetic headphones stay AWAY from OTL amplifiers,they don't like low impedances.You want a Transformer Coupled tube amp for Planars..IMO a pure Class A solid state DAC/PreAmp/Head amp gets you everything a good tube amp does + better bass control & yes I've owned several tube amps but am now a Class A SS convert..Burson Audio makes some VERY organic sounding Class A gear & also Topping is doing some damn fine work as well...

I love the sound of my Woo Audio WA5LE with my Sennheiser HDV820 I also have the Focal Utopia, Hifiman HE1000-SE, Meze Empyrean & the Sony Z1R. All are very good, but for some reason I keep going for the HDV820s.

I use a Wyred 4 Sound DAC with the Fempto clock option.   It was a major step up from anything I have heard before, either in my system or at a dealer.   It is not the least expensive way to go but it is a good one.

My headphone recommendation is for Stax electrostatics. I have used them for many years and appreciate their clear, fast sound. As far as the price, there are many combinations of phones and amps to choose from. As an example, today on Audiogon I found a used pair of Stax 404 phones, with a tube amp (Stax, of course) for around $800. That leaves room in your budget for a transport and DAC. 

Thanks @soix for the thoughts and ideas. They're right on I think. I just bought a pair of HifiMan Sundara phones to try out, and since they're middle of the road I can start there and determine if they are "good enough" or if I want to try something upwards from there. 

I'm also going to start building the DAC/Amp side of things and I think I'm starting to understand it...

At your budget I’d shy away from a tube amp if you’re looking at planar ‘phones. While you can certainly build a very decent headphone rig for $2k, IMO if you can up it closer to $3k you’ll be at a significantly higher level of performance. Also, to keep costs down at least for now and if you have decent WiFi, I’d recommend running a USB cable from your phone or tablet (running Qobuz) to a DAC so it can handle the source/streaming functions until you can justify a better dedicated streamer. So, here is an idea for a pretty excellent headphone setup given what you’re looking for...

• Hifiman Arya open-back planar headphones - $1599
  
• Singxer SA-1 Class A headphone amp/ preamp - $599
  
• Musician Pegasus R2R DAC - $1100

Just my initial stab at it FWIW, but there are other great alternatives to each of the above depending on your particular tastes. I think this system would synergize well and provide an expansive soundstage (for headphones anyway) with very good tonality and excellent and refined upper-level detail. Hope this helps, and best of luck building a satisfying system.

Thank you - I'm having some difficulty understanding what components are actually needed. Since I have essentially zero music source (CD, Vinyl, etc.) I'd likely just be buying music at a monthly cost, i.e. Tidal or qobuz I guess? Then I need to figure out whats the right way to get that material into a DAC->AMP->headphones? This is where I'm a bit confused, and hence my questions about what a "system" looks like. I.e. a fully functioning music listening experience on a table. 

Stax was one set I was looking at, and I'd like to try them out...

Stax electrostatic headphones with the Stax power supply and amplifier.   I used them almost every day when the kids were small and went to bed early.  I have an older set, which in today's dollars would be roughly equivalent to the SR-L700 MK2.  If you can afford them, look no further!  They have held up amazingly well after all these years - ZERO failures or problems!