To whom landed here from Google searches and might have a simmilar dillema - some explanations below.
First, my rationale: I wanted clear, articluate, punchy bass. Therefore, I went for a floor-stander that goes down to 20Hz. Or at least to 25Hz. And I don't mean the 25Hz written in the spec sheet (-10dB/1m), but the one in tests, with room response at -6dB/2.5m.
Further on, I looked for an amp that can sustain and control that bass. That is - at least 200W into 8 ohms which must double into 4 ohms.
Also, for crystal-clear vocals and sparklinkg instruments (piano, violin, guitar), one must go for the best mid-range there is (usually only found in the reference series of speakers).
Therefore, for top-notch sound in the bass and mid-range, you'd want a "flagship", "higher-end", "signature", "reference", "top of the line" amplifier and speakers, plus cabling, room treatment and good speaker positioning.
Here are the finalists - partially extracted from StereoPlay's latest rank (June 2019) combined with my personal research.
Reference class A/B amps with DAC and at least 200W/8 ohm which doubles into 4 ohms (approximate MSRP prices):
- Gryphon Diablo 300 (18k with DAC)
- Mark Levinson Nº 585 (14k)
- McIntosh MA9000 (13k)
- Hegel H590 (10k)
- Maranz PM10 (Class D, 10k)
- Audionet DNA (10k)
- Perreaux 255i (8k)
- Krell Digital Vanguard (7.8k)
- Anthem STR (6k)
- Hegel H390 (6k)
Reference Speakers that in-room go below 30Hz at -6dB/2.5m (approximate MSRP prices):
- KEF Blade Two (25k)
- Bowers & Wilkins 802 D3 (22k)
- Canton Reference 1K (20k)
- Monitor Audio Platinum PL500 II (20k)
- Focal Sopra No. 3 (20k)
- Audio Physic Avantera III (20k)
- Dynaudio Confidence 30 (20k)
- KEF Reference 5 (19k)
- Sonus Faber Amati Tradition (18k)
- Bowers & Wilkins 803 D3 (17k)
- Wilson Audio Sabrina (16k)
- Focal Sopra No. 2 (14k)
- Focal Kanta No. 3 (13k)
- Canton Reference 3K (10k)
- Dynaudio Contour 60 (10k)
- Nubert nuVero 170 (9k)
- Bowers & Wilkins 804 D3 (9k)
I got (May 2019) a Hegel H590 + Canton Reference 3K combo for ~9k euro (MSRP 20k) and they sound heavenly
The Canton Reference 3K in-room goes just a bit below 30Hz - but for lower bass I had to spend more - much more
The Hegel H590 best matched what I was searching for because of its detailed, neutral, crystal-clear DAC/amp and bass control. Also the lack of phono amp, headphone amp, tone controls, fancy/gloomy aesthetics and other features that I don't use/need - instead, the H590 focuses only on the things that matter to me the most: detailed sound, musicality, bass control, dynamics (it can deliver up to 2.2kW per channel into 1 ohm!), noise floor, quality DAC, basic streamer, minimal design etc.
Note that I listen mostly to acoustic music - jazz, ambient, chill-out, piano, instrumental and classical in a 25 square meter room.