1 -Gotcha. Just a strange market. Many of the amps suggested are not in production anymore..
2 -Also many suggestions are amps sold from web sites that look like guys making them in there garage.
3-None of the amp company's have phone numbers ( email service only)
4- many say $500 tube amp is all you need
5- lastly, many say it will be hard getting a lot better sound than my Asgard 2
So yes it's easy to change my mind with such a confusing niche market.
Headphone land is a wild ride. Some take a minimal approach, some brag how big their wallets are and how much they've spent and some justify their purchase
We are all having fun at the end of the day. Price is something that does not necessarily mean will be superior or better. Our ear are so subjective.
Are you looking for an amplifier "only" ???? What DAC are you using?????
I'd say in many cases the DAC has more weight in the final sound signature more so than the amplifier. However when you start talking about vacuum tubes the sound signature can potentially(pushing the limits of calling it generalizing) have more high frequency roll off and maybe even less bass slam.
If your truly a detail freak I'd suggest looking into DAC's that have the ESS sabre 9018 chipset. I prefer Burr Brown DAC's due to less hyper detail and possibly more analog sound.
Try pick up a Concero HD DAC that has hyper details with very distinct instrument separation. I sold my Resonessence labs Concero HD because it was gave me too much detail that made me analyze music rather than enjoy it.
I keep my modified HD800 simply because I own it and it sound very nice for some music when I'm in certain moods. I have the HD650 and HE560 that really is my goto HP for non critical enjoyment of music that does not throw me into a headphone world of extreme hyper detail. Tubes and HD800 suites my ears much better than using solely solid state.
If your spending decent coin on a pair of headphones I'd suggest playing with different combos of DAC's and amps. I will say my modified HD800 sound the best to my ears with my Tube dac setup and even with the "CHEAP" 02 objective amp. I'd listen and enjoy that combo over my Burson virtuoso with burr brown dac chipset. Combo of components and speakers/headphones is all about synergy of the combined/complete system.
I'd start looking at different DAC's before buying new amps