I will be purchasing a pair of M5HPs soon and I have a question about amplification. I would like to drive these with a moderate cost integrated amp. Would a Marantz model 50 pure analog stereo integrated amplifier (70 x2) be sufficient to push these speakers?

That would be more than enough to drive them.

I'm using a Yamaha RX-V681 and a Yamaha RX-V673 to drive mine (different set-ups) and am not close to using all the power to play 75-85 db. The Yamahas are rated at 95w. I have a sub on both systems, but frequently turn it off on the V673 system.

Bottom line if you're using a sub then absolutely enough power; if no sub, them most likely enough power.

It´s enough to fill a mid sized room to reasonable listening levels without distortion. But not enough to play highly dynamic material at loud volumes (without clipping). IMO of course

If you haven't bought the Model 50 yet (and it's quite a beauty), I'd also consider going multichannel AVR. You'd lose the phono stage, but you'd be future proofing your setup with 4K/8K HDMI switching, eARC, Hi-Res DAC, bass management, room correction algorithms, and perhaps streaming playback.

While there could be an audible difference in stereo playback between an integrated amp and AVR, I'd be hard pressed to notice a difference.

Integrated amps were a minimalist solution to pre-amp and amplifier separates; receivers and later AVR's became even more minimalist by going all in, all out, as an all-in-one wonder. The best way to lighten up is to find these heavy hitters.

Thank you all for your response. Hope to place and order soon