Good Amp for Martin Logan Monolith II

Get a McIntosh Mc-2300 7270 or 7300 300/watts/ch 1500-2000 in excellent condition and will drive any impedance curve the Monoliths can through at it

ARC is also a great amp for the Monoliths but they will be pricier being tube amps with the same output

You may want to consider Bi-amping the Monoliths they do sound better with an electronic crossover configuration

The one thing you might watch with Mac's is they have autoformers to handle the impedance curve so you might want to consider how many added curcuits you want in the signal path.I am also interested in the responses to this as I have a pair of SL3's and thinking of changing amp's.

If you want good sound from your Monoliths get tubes.
Everything shows up for sale eventually. You have to decide on what you want and be patient.
When buying used equipment there is no other choice. I don't like buying substitutes with anything whether it is stereo equipment or a dish for my cat. I would rather do without.

I agree with Rrog and go with tubes,but if you want to stay with solid state maybe check out Mccormack,Belles and
Classe;although the Sanders/Innersound amps are tough to beat as well.

Find a used Mark Levinson 23 or 23.5 or 27.5 and you are there. I have an Audio Research REF 3 pre-amp that goes to two AR VTM 120 Monoblocks for the upper panels of my Monolith IIIs and a Mark Levinson ML3 for the bass drivers.
I also use an ultra modified Bedini 250/250 MK II (that I modified) and it is also wonderful on the upper panels. Do not, I repeat, do not let tube bias steer you away from excellent and cost effective sound.

The ML 23.5 is still one of the best amps out there and for the money, you can't touch it tube or solid state.

enjoy