To Tube or not to Tube, that is the question

If you love music and sound definitely experience a true tube amplifier.  A lightly used rogue audio cronus magnum ii should easily be in your range.  

the sound will surpass any current amp you have, the cm sound amazing and have plenty of power, dynamics and authority for your speakers.

you will hear an open, clear dynamic sound.  the sound stage will be large in all directions.  it will be an atmospheric sound, pure in tone and tambre and highly refined and smooth.  vocals and instruments will sound natural and catch your interest, they will seem to float in space.  you need to hear it.  good luck!

I've been quite pleased with my LSA VT-70 from Underwood HiFi, an online retailer. 35 watts/channel with EL34 output tubes (and it will also accept 6550 or KT88 outputs.) They are currently $1,300 plus shipping. 

To tell you the truth, your Sphinx is getting you 99% there. Tube gear takes a few more bucks to own and operate and you'll need some really nice tube friendly loudspeakers to go with the tube amps. My favorite tube set-ups featured Triangle floorstanding loudspeakers.

Great recommendations above. 

I agree that you should look at China Hifi.  Just be sure to watch the voltage specified with the amp. If you're in North America, you'll want 115/120v.  

I've owned and built all sorts of tube amps.  Willsenton and Doge are amazing amps regardless of the price/country of manufacture.  

What tubes are you using in the Sphinx. It makes a difference. I am using a Sphinx v3 as a preamp with NOS Brimar 12au7's with an Orchard Audio GaN FeT amp and the sound is exceptional.