1)The Monoprice Liquid Platinum ONLY BALANCED. The SE rca's are not that great (Amir reviewed it a few years back, but no xlr in/xlr out. I would also recommend using it with only a 200-600ohm headphone due to the volume knob. Catch it on sale for $400-$500.
2) Rebel Amp. Its not a tube, but VERY warm, and has the smooth treble roll off, and 2nd harmonic that is typically deemed "tube-ish". Its big and green though, but excellent. $500
The Flux Fa-10/12 etc have similar smooth, warm sounds too, but are $750. They are cleaner and the response is more linear than the Rebel.
3) If you want to spend more money, maybe an Auris or Feliks. Both are wonderful sounding tube amp and have somewhat less noisy playback.
4) Cheaper, maybe a dark voice, or a xduoo TA-20 but they can be noisy, with lower impedance headphones.