bedroom system need quality at low volume

Getting rich sound and good imaging at low levels is hard to do in general because of the Fletcher-Munson law. It was discovered many many years ago that human hearing is less sensitive at both ends of the frequency spectrum as the absolute volume decreases. This is a survival tactic/strategy so we can better hear the sound of approaching predators, which is generally in the midrange ;--)

If your preamp or receiver has a "loudness control" and you engage it, then as you turn down the volume, it will automatically boost the high and low end at a slowly increasing rate to compensate for Fletcher-Munson loss.

Two other things that can help are using highly efficient speakers, or electrostatic speakers (stats aren't that efficient but have extremely light-weight diaphrgms.) Inefficient speakers, or speakers with heavy cones/panels (like Maggies for instance) don't provide uniform response (or sometimes ANY response!) at low levels.

A Watt is the product of Current times Voltage. So not all (individual) Watts are created equal. Choosing whether you want more voltage or more current in each of your amps' output Watts should be based on the load the amp will be driving. Electrodynamic transducers (ribbons, voicecoils, and planar-magnetic) need as much voltage as possible in each Watt; electostatic transducers don't permit the electrons to flow (Current) as the (static) voltage increases/decreases, so they would prefer as much current as possible in each watt.
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"The whole stage" implies wide frequency range, to me. Small bookshelves will be limited in frequency range by definition. My wife actually preferred narrow floor standing speakers rather than bookshelves, so consider them if you can. Or, a small sub in the corner helps round out the lower frequencies. I use a small REL with Von Schweikert VR-1s and am extremely happy. If you use a lower watt amp/integrated you will actually have better control over the volume at lower levels. Using very efficient speakers may make the volume harder to control. The least obtrusive bookshelves are the Gallo spheres. Matched with their sub they are a great combination, take little space and you can have 30-20k Hz. Good luck and have fun!

I am using Spica TC-50s in my bedroom, and couldn't be happier. They excel at sounding great at low volume; on the other hand, they don't get very loud. As you crank the volume knob past a certain point, they stubbornly refuse to get any louder. If by whole stage, you mean full frequency range, you might want a sub with the Spicas. I have mine paired with a JJ828 integrated and Sony XA777ES. The JJ is great for (among other reasons) having a remote control power switch, so you can shut it off without getting up.

To me "whole stage" has nothing to do with full frequency range, it has to do with creating a realistic holographic image with a palpable soloist (vocalist or instrumentalist) in the center, and the other performers/instruments in their proper location.

This does NOT require a full frequency range, but rather a signal free of any time smear due to crappy IC's and speaker cables, and a speaker with strong and accurate midrange rendering (efficient cones, small ribbons, or small stats.) Spicas (on stands?) would make great bedroom speakers ;--)

The brain cannot detect the location of frequencies under 100Hz, and most average sized bedrooms (10 x 13 to 12 x 16) cannot support frequencies below 35 -- 45 Hz anyway. So a very small, limited low-frequency-extension sub might be desirable; but not mandatory if your main speakers go down to at least 40Hz.

Most bedrooms are full of highly absorbent surfaces and furniture, so very little (if any) audible high frequencies will make it to the pillow ;--) However, a high quality dome or ribbon tweeter (or a stat of course,) will contribute to the production of audible lower frequency harmonics, and should be considered in your speaker selection.