Integrated Recommendation

I was also thinking about the Rogue Sphinx. Would seem to be a very good fit at the price point. I have not heard that unit specifically yet but am a fan of the tube/Class D hybrid approach and Rogue's amps that I have heard in general. Rogue tends to offer top notch value for tube amp gear.

The ROgue specs I've read indicate doubling power output from 100 watts into 8 ohm to 200 into 4 ohms. That's not a guarantee but a good omen for getting good performance out of the Manis.

Class D amps require less beefy power supplies in order to do that than most amps which makes ones that do good candidates on paper for demanding loads on a budget.

But the Manis are only 85 db efficient, so yes, ability to go louder and clear could be limited.

You would probably have to go used to do better/go louder. The more powerful MF would be a good choice for that.

Frankly, I think you might be better off going with a used power amp and separate pre-amp with hard to drive speakers like the Manis. Integrateds, especially less expensive ones, tend to not have the beefy power supplies needed for high power and current delivery. Class D integrateds, like those from Wyred maybe, might have the best chance and might be had used.

For separates, you might for example try a d-sonic class D amp used or new and match that to an affordable separate pre-amp within your price range.

I'd shoot for whatever you can find in your budget that features a 250w/ch power amp or more if possible, plus good current delivery ability. That's the main and most straightforward thing to get right first.