Best Headphone system under $1000???

You can get more ideas from reddit
https://www.reddit.com/r/headphones

If you want to try more headphones I recommend Beyer Dynamics. Dt1990 is said to be very good and details. I have the Amiron Home which are a bit softer. They are both probably better than your HD6xx but not as good as the Elex.

I was able to buy Cary HH-1 and Sennheiser HD 700 for less than $1,000 in total, each new from manufacturer just by keeping an eye out and jumping when the opportunity arose. Cary had a flash sale on the HH-1 for Christmas 2017...

I am quite impressed with the combination. When they died, I replaced the stock Electro-Harmonix 6922EH with Genalex -Gold Lion E88CC/6922 for marginal improvement in tonal qualities.

Most people find these Sennheisers too bright, but this amp curbs that in just the right way. The sound is lively, tight bass, revealing and seemingly neutral while still having that tubey je ne sais quoi. 

The Elex will be effected by the amps output impedance more than the HD6XX (80 ohms vs 300)

As the output impedance goes up the bass will get louder (also effects damping) and this is probably not what you want with the Elex as it is already a little warm. Typically tube amps have higher output impedances than solid state amps but there are no absolutes.

I have never tried mine on a tube amp and honestly I am not to up and up on my tube amp knowledge.

Here is a detailed article on amp impedance’s effect on headphones.

https://www.innerfidelity.com/content/musings-headphone-amplifier-output-impedance

Grado RS-1s with their battery powered pre-amp.

Enjoy a great hobby, here’s my two cents...

I currently have the HiFiman Anandas, they are right at the 1k price point.  They are huge, but light weight.  Sound is amazing, best I’ve owned.  They can run easily off a phone but as with most, sound better with better DACs/Amps.

I’ve had Audeze LCD-X (way too heavy, ok sound), the Massdrop HD-6xx (ok but un-dynamic sound, no-go with a phone), and still own as a back-up Audioquest Nightowls, which sound great but have been discontinued as Audioquest got out of the headphone business.  They are a great used bargain if you can find them, usually $150.00 to $200.00.

Just for info, I use a Mytek Brooklyn DAC+, which is a DAC/Amp combo, and listen through a balanced set-up.  Source is a Dell Desktop Windows 10 with Tidal, and more recently Qobuz, as my music sources, both at the highest quality available.  I have a LG V30+ Android phone and an Audioquest Dragonfly DAC/Amp that I sometimes use for late night listening, often wirelessly with Bowers and Wilkens PX noise cancelling headphones.  The phone transmits the high quality Apt-X HD version of Bluetooth, which the B&W headphones accept.  Very happy with the SQ of the headphones, but they could use a bit bigger earpieces for my big ears!