great dynamics at a med-low volume?

You're whole system has to contribute to this. Its not something that can happen by just getting a new pair of speakers.

Most Studio monitors have what you are looking for . Passive or active . Seek them out and give a listen. If you go passive it is harder to find the right amp to go with them . I would personally go with the actives . They are already set up for optimal sound. You will be amazed at the low level detail . Even at the beginning starting price of a few hundred dollars .

Looking up your amp I see it outputs 300W @ 8ohms so I imagine what I'm presently breaking in would do: Clearwave Duet 6 monitors. They're rated at 85db efficiency and you will have the power to move them. They pack a hell of a lotta punch for their size.

They can put out at low volumes but the span to high volumes can be seem a short distance as they come alive rather quickly. The dynamics can be off putting at first as they're fairly flat for most of the spectrum so when the mids and bass assert themselves, it can surprise and/or shock you (which can be pleasurable).
Some recordings with more headroom than normal will amply demonstrate this.

All the best,
Nonoise

one other point on the active monitors is .At any volume they are hard to get to distort. they do not turn to crap when volume is raised .

Ref 3 a dulcets

I have your amp and use soundfield audio m1's. I bought them specifically for low level listening. However if I want to turn them up or watch a movie these speakers will litteraly shake my room. Contact Aj @ Soundfield audio.

"02-01-15: Maplegrovemusic
Most Studio monitors have what you are looking for . Passive or active"

What monitors have you tried? I tried some actives myself. They work OK, but I wouldn't buy them again.

Triangle Titus XS are top notch at low to moderate volume.

http://www.silbatoneacoustics.com/labsystems.html

Zu Audio is the most dynamic speakers and works very well on low volume. You can find bookshelf models as well.

What does your budget and listening room look like?