headphones for tube system

Thanks - but this appears to be just a cheap marketing site

Why would you say that?  It's mostly hobbiests that are willing to help or answer any question...  sometimes you need to give it some time.   I looked at your pre, it looks like there are hi level and lo level pre outs.   Ideally a fixed level output like a tape out is best to drive a headphone amp.   Some phones like Stax use the amplifiers speaker terminals to drive the amp.   

Honestly headphones are an extremely personal item... what I think is great may not appeal to you at all.  Having just purchased headphones the only advice I will give is to demo a bunch.  Like speakers , they all have different sound signatures.  

I just bought a pair of Grado RS2e and I love them,  others may not care for them at all.   

Thank you for your suggestion, I shall be investigating further and demo-ing some options within my price range.
Re my comment  - did you see the link ? I believe it has now been deleted by Audiogon so I feel vindicated.
Regards
Xian

Looks like your preamp has analogue outputs(hi & low?)...If your using rca interconnects you could go with balanced I/C between amp & pre and use pre out to a headphone amp.Some expensive headphone amps have balanced inputs should you care to spend that much $...
As for head amp and cans I suggest you spend time going through the equipment reviews on "head-fi.org"...Headphones are a lot like speakers,ie:you have cans with the highly detailed sound,the romantic sound and the studio sound...Also figure out a budget.Headphones can top out at $100,000.00+...Best value for $ IMO is the $250.00-$750.00 range with HiFIMan,Audeze and Sennheiser’s new HD660 leading the way...

I use inexpensive Grados (SR80e) that replaced my unfixable old SR60s…the 80s took a while to break in (too much treble initially) but after a week or so they became astonishingly good, and when I've considered replacing them with other more expensive models from other brands (tried several here and there) I just stay with my Grados. I have closed back phones for recording, but the Grados get my reference choice.

Stax.

Any update?

+1 for Grado RS2e