Low-Powered Tube Amp for Zu Soul MkII?

I'm totally new to tube gear, but I just got a new pair of Zu Soul Mark II speakers, and I think my old solid state integrated might need to be replaced with a tube amp. I've been reading that these high-efficiency speakers really like lower-powered tube amps, and I'm wondering if anyone here has experience with them. Here are my constraints:

I have a small room.
I'd love to get something that's made in the 'ol USA.
Preferably around or below $2K.
It would be ideal if it could fit inside our existing cabinet, which is 17.5" deep (this rules out the Cronus and maybe even the Sphinx, unless I make some huger changes).

I love the look of the Rogue Cronus and maybe the Sphinx even more, and these prices are conceivable. But one of my conditions is that I need to be able to hide all this stuff, and my cabinet's too small depth-wise for some of these bigger amps, sadly.

Thanks for any suggestions!