Amps under $5k that are resolving at low volumes?

You can easily get a Pass INT-30 or INT-150 for under $5k used here on Audiogon.

You won't be disappointed. If you have your room and speakers acoustically optimized and well set up, I'd recommend the INT-30 as it recreates the acoustic venue the performance was performed - better than the 150. The INT-150 is more dynamic.

If you Prima Luna has pre-outs, and if that piece will perform to your level of expectation (I have no experience with this piece), you can get a Pass XA-30.5 also. We used one with our moderately high end system for a few years and enjoyed it. It really is an over achiever.

Kindest regards, TJF

Isn't this more a function of the speakers?

I would tend to agree with Zd542 about the speaker being the issue. After moving from a private home in the suburbs back into a city apartment I also looked for a system that I could enjoy at lower volumes. What I discovered in my research was that this seems to be more a function of the speaker than the associated system. There are not many speakers that really play well at low volumes.

IMHO the best speaker that I heard at low volume was the Harbeth SHL5. I heard a few others like the Vandersteen Treo and VLR Wood that sounded almost as good at low volume but the Harbeth stood out from the group. I had foolishly sold my Super HL5's years ago but I lived with them for more than 2 years. I ended up with the Vandersteen VLR Wood and though not quite the equal of the Harbeth, it is still a very enjoyable speaker at a much lower price point. YMMV.

I suggest you talk to your Magnepan dealer about your dilemma as he may have suggestions specific to your speaker.

"03-15-15: Robr45
Isn't this more a function of the speakers?"

No. All of the components contribute. Not only that, but you can have a situation where one component can stop all the others from performing to their potential. For example, I have an amp that doesn't image well. When I put it in a system that otherwise has components that excel in imaging, the whole system is brought down to the level of the amp. It makes it sound like all of the components have an imaging problem.

I would concur that the Maggies may be the main factor with the low level resolution.
Having owned 3 different pair, low level detail is not what they are about.
If you are after low level resolution I would recommend full range electrostatics or horns.