Best Mid Fi Amp from 90s to today. Look

You don't mention your speakers, other gear or music preferences. Here's what I've heard...

The Marsh is a terrific amp and affordable too. It powered a friend's ML Ascents to excellent effect, a tonally accurate , musically realistic amp.

Another acquaintence has a Spectron Musician paired with Dunleavy IVs - very impressive when I heard it. More watts than the Marsh if your bass drivers require more power and damping. If you have electrical issues at your house, I've heard that digital amps can be sensitive to crud in the lines.

Your amp selection seems to lean to warmish amps...have you considered Bels???

Really, your speakers' power requirements plus your personal taste, other elctronics, room etc. all enter into the equation.

I used to own a Meridian 557, I had no complaints with it!

I am not familiar with all of these amps, but I can share my personal experience with the B&K M200 Sonata mono blocs. They are extremely robust, using 10 pairs of hi-current MOSFET output devices. MOSFETS typically sound sweeter than bipolar devices, and have been likened to tube like sound, but with the current drive and tight fisted control of solid state. MOSFETS also love heat, and can take a lot of punisment. For example, the M200s will deliver 150 amps p-p of current, which means that they easily handle complex loads and can drive very low impedances at full power (read loud). For example, they work very well with inefficient and current hungry ribbon drivers. Combine that with a Class A predriver frontend, selectable balanced/unbalanced inputs and they offer an amazing value. Excellent bass, deep soundstage, glorious open midrange (vocals are palpable) and an extended but polite high end, they seem to get it all right. As a testament to their robustness, B&K used to offer factory rebiasing to allow the amps to run up to 100watts in Class A. I took advantage of their offer and had mine rebiased. As a result, they run a bit warmer, but it pays dividends in the sound- especially noticeable on delicate passages, vocals, and jazz combos. They really open up. Also, only about a 15 minute warm up time before they sound effortless. I used them with tube preamps from Moscode and ARC. A great combination. Why am I selling them? I am taking a leap into tubes.

I would like to put my two cents in if nobody minds. The Marsh A400, Aleph 3, and Rogue amps get my vote. We are fortunate in this day and age that there are quite a few great midfi amps to choose from. You don't necessarily have to spend megabucks for good sound any longer.