Tube integrated with real bass. Does it exist?

Its worth noting that they may be all you have to go with but efficiency specifications are quite loosy goosy typically and hard to bank on either way.

Usually, if speaker is small, chances are bass will be limited with most tube amps. Those speakers that can do extended flat bass out of a small box always require more power and current to achieve it. No free lunch here that I have ever seen or heard. If it appears too good to be true, it probably isn't. if you punt on the extended bass aspect of things though, things become pretty easy. Low bass is where all the hard work happens ie large efficient drivers and or smaller drivers and more power/current to move them. Its basically the limitations of physics that cannot be undone even with the best and highest quality designs.

Cronus Magnum is respectable with most speakers I have heard it with. Use a powered sub or two with it (or most any tube amp) and cross it over properly and you are golden.

+1 to the Prima Luna Dialogue Premium integrated with KT-150's. Unless you are a pipe organ enthusiast you will do just fine. If you want accurate bass below 30 hz, plan on spending the cost of a small cottage

Give Mapleshade a look. There are some HH Scott integrated (EL 84 tube) amps they modify that may fit the bill. Read their description and user comment sections.

Jadis DA60 integrated has absolutely impressive low-end slam.

It's a honey of an amplifier. I've own/ed a lot of amplifiers, tube and solid state. Top to bottom, it's the best I've had in my system.

I would guess the DA88S replacement would follow-on in regard to its bass.